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TECUMSEH
T E C H N I C I A N ' S H A N D B O O K
This manual covers engine models:
OHH50 - 65, OHHSK50 - 130, OHV11 - OHV17, OVM120,
Other illustrated Tecumseh
For complete listing write or call
CONTAINS SEARS CRAFTSMAN CROSS REFERENCE
ENGINES 
CONTENTS
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Tecumseh Products Company
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ii
CHAPTER 1 GENERAL INFORMATION
ENGINE IDENTIFICATION
Tecumseh engine model, specification, and serial numbers or date of manufacture (D.O.M.) are stamped into the blower housing, or located on a decal on the engine in locations as illustrated (diag. 1 & 2). The engine identification decal also provides the applicable warranty code and oil recommendations (diag. 2).
Interpretation of Model Number
The letter designations in a model number indicate the basic type of engine.
OHH |
- |
Overhead Valve Horizontal |
OHM |
- |
Overhead Valve Horizontal |
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MediumFrame |
OHSK |
- Overhead Valve Horizontal Snow King |
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OVM |
- Overhead Valve Vertical Medium Frame |
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OVRM |
- Overhead Valve Vertical Rotary Mower |
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OVXL |
- Overhead Valve Vertical Medium Frame |
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Extra Life |
OHV |
- |
Overhead Valve Vertical |
The number designations following the letters indicate the basic engine model.
The number following the model number is the specification number. The last three numbers of the specification number indicate a variation to the basic engine specification.
The serial number or D.O.M. indicates the production date of the engine.
Using model
OHV Overhead Valve Vertical
16Indicates the basic engine model.
204207A is the specification number used for properly identifying the parts of the engine.
5215C is the serial number or D.O.M. (Date of Manufacture)
5 is the last digit in the year of manufacture (1995).
215indicates the calendar day of that year (215th day or August 3, 1995).
C represents the line and shift on which the engine was built at the factory.
Emissionized engines that meet the California Air Resource Board (C.A.R.B.) or the Environmental Protection Agency (E.P.A.) standards will include additional required engine information on the engine decal.
NOTE: To maintain best possible emission performance, use only Genuine Tecumseh Parts.
ENGINE MODEL
NUMBER
1
THIS ENGINE MEETS
CALIF. EMISSION REGULATIONS FOR
ULGE ENGINES AS APPLICABLE
FUEL: REGULAR UNLEADED OIL : USE SAE 30
OHV 125 203000A |
(D) |
RTP358UIG2RA |
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358cc |
3057D |
2
1
SHORT BLOCKS
New short blocks are identified by a tag marked S.B.H. (Short Block Horizontal) or S.B.V. (Short Block Vertical). Original model identification numbers of an engine should always be transferred to a new short block for correct parts identification (diag. 3).
THIS SYMBOL POINTS OUT IMPORTANT SAFETY INSTRUCTIONS WHICH IF NOT FOLLOWED COULD ENDANGER THE PERSONAL SAFETY OF YOURSELF AND OTHERS. FOLLOW ALL INSTRUCTIONS.
FUELS
SBV OR SBH IDENTIFICATION NUMBER
SHORT BLOCK IDENTIFICATION TAG
SBV- 564A
SER 5107
SERIAL NUMBER
3
Tecumseh Products Company strongly recommends the use of fresh, clean, unleaded regular gasoline in all Tecumseh Engines. Unleaded gasoline burns cleaner, extends engine life, and promotes good starting by reducing the build up of combustion chamber deposits. Unleaded regular, unleaded premium or reformulated gasoline containing no more than 10% Ethanol, or 15% MTBE, or 15% ETBE may also be used.
Leaded fuel is generally not available in the United States and should not be used if any of the above options are available.
Never use gasoline, fuel conditioners, additives or stabilizers containing methanol, white gas, or fuel blends which exceed the limits specified above for Ethanol, MTBE, or ETBE because engine/fuel system damage could result.
Regardless of which of the approved fuels are used, fuel quality is critical to engine performance. Fuel should not be stored in an engine or container more than 30 days prior to use. This time may be extended with the use of a fuel stabilizer like TECUMSEH'S, part number 730245.
See "STORAGE" instructions in the Technician's Manual, Operators Manual, or Bulletin 111.
ENGINE OIL
TECUMSEH FOUR CYCLE ENGINES REQUIRE THE USE OF A CLEAN, HIGH QUALITY DETERGENT OIL. Be sure original container is marked: A.P.I. service "SF" thru "SJ" or "CD".
TECUMSEH RECOMMENDS USING ONE OF THE FOLLOWING FOUR CYCLE OILS THAT ARE SPECIALLY FORMULATED TO TECUMSEH SPECIFICATIONS.
DO NOT USE SAE10W40 OIL.
FOR SUMMER (Above 320 F) (0oC) USE SAE30 OIL. PART #730225
Use SAE30 oil in high temperature, high load applications. Using multigrade oil may increase oil consumption. FOR WINTER (Below 320F) (0oC) USE SAE5W30 OIL. PART #730226
(SAE 10W is an acceptable substitute.)
(BELOW 00F
NOTE: For severe, prolonged winter operation of HH120 model, SAE10W oil is recommended.
Capacities
Engine Model |
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Oz. |
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ml. |
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OHH,OHSK |
21 |
630 |
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OVRM 40 - 6.75 |
21 |
630 |
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OVRM105 & 120 |
21 |
630 |
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OHSK80 - 100 |
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26 |
720 |
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OHM, OHSK 110* - 130 |
32 |
960 |
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OVM 120, OVXL 120, 125 |
32 |
960 |
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OHV 11 - 13 without oil filter |
32 |
960 |
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OHV 11 - 13 with filter |
39 |
1170 |
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OHV 13.5 |
- 17 |
without oil filter |
55 |
1650 |
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OHV 13.5 |
2 1/4" filter (part # 36563) |
62 |
1860 |
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OHV 13.5 |
2 5/8" filter (part # 36262) |
64 |
1920 |
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* NOTE: Model OHSK110 with a spec. of 221000 and up, have a capacity of 26 oz. (720 ml.)
2
Oil Change Intervals: Change the oil after the first two (2) hours of operation and every 25 hours thereafter (OHH &
NOTE: The oil filter (if equipped) requires changing every 100 hours or more often if operated under dusty or dirty conditions.
Oil Check: Check the oil each time the equipment is used or every five (5) hours of operation. Position the equipment so the engine is level when checking the oil.
CAUTION: Remove the spark plug wire before doing any service work on the engine.
Oil Change Procedure: Locate the oil drain plug. On some units this plug is located below the deck through the bottom of the mounting flange. Other units drain at the base of the engine above the deck or frame. On some rotary mower applications, where access to the drain plug is restricted by the equipment, it may be necessary to drain the oil by tipping the mower in a position that would allow the oil to drain out of the fill tube.
On units that the drain plug is accessible, remove the plug and allow the oil to drain into a proper receptacle. Always make sure that drain oil is disposed of properly. Contact your local governing authorities to find a waste oil disposal site.
Once the oil is drained, reinstall the drain plug and fill the engine with new oil to the proper capacity.
NOTE: Today's fuels can cause many problems in an engines performance due to the fuels quality and short shelf life. Always check fuel as a primary cause of poor engine performance.
The following is a minor
engine's performance remains poor. |
STANDARD |
OHV |
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CAUTION: Remove the spark plug wire |
PLUG |
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before doing any service work on the engine. |
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1. |
Service or replace the air cleaner. See |
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Chapter 2 under "Service". |
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2. |
Inspect the level and condition of the oil and |
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change or add oil as required. |
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3. |
Remove the blower housing and clean all dirt, |
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grass or debris from the intake screen, head, |
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cylinder cooling fins, carburetor, governor |
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levers and linkage. |
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4. |
Make sure the fuel tank, fuel filter and fuel |
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line are clean. Replace any worn or damaged |
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governor springs or linkage. Make the proper governor adjustments and carburetor presets where required.
5.When replacing the spark plug, consult the proper parts breakdown for the spark plug to be used in the engine being serviced. Set the proper spark plug gap (.030") (.762 mm) and install the spark plug in the engine. Tighten the spark plug to 21 foot pounds (28 Nm) of torque. If a torque wrench isn’t available, screw the spark plug in as far as possible by hand, and use a spark plug wrench to turn the spark plug 1/8 to 1/4 turn further if using the old spark plug, or 1/2 turn further if using a new spark plug.
6.Make sure all ignition wires are free of abrasions or breaks and are properly routed so they will not rub on the flywheel.
7.Properly reinstall the blower housing, gas tank, fuel line, and air cleaner assembly if removed.
8.Make sure all remote cables are properly adjusted for proper operation. See Chapter 4 under "Speed Controls and Linkage".
9.Reinstall the spark plug wire, add fuel and oil as necessary, start the engine.
3
STORAGE (IF THE ENGINE IS TO BE UNUSED FOR 30 DAYS OR MORE)
CAUTION: NEVER STORE THE ENGINE WITH FUEL IN THE TANK INDOORS OR IN ENCLOSED, POORLY VENTILATED AREAS, WHERE FUEL FUMES MAY REACH AN OPEN FLAME, SPARK OR PILOT LIGHT AS ON A FURNACE, WATER HEATER, CLOTHES DRYER OR OTHER GAS APPLIANCE.
Gasoline can become stale in less than 30 days and form deposits that can impede proper fuel flow and engine operation. To prevent deposits from forming, all gasoline must be removed from the fuel tank and the carburetor. An acceptable alternative to removing all gasoline, is by adding Tecumseh's fuel stabilizer, part number 730245, to the gasoline. Fuel stabilizer is added to the fuel tank or storage container. Always follow the mix ratio found on the stabilizer container. Run the engine at least 10 minutes after adding the stabilizer to allow it to reach the carburetor.
Draining the Fuel System
CAUTION: DRAIN THE FUEL INTO AN APPROVED CONTAINER OUTDOORS, AND AWAY FROM ANY OPEN FLAME OR COMBUSTION SOURCE. BE SURE THE ENGINE IS COOL.
1.Remove all gasoline from the fuel tank by running the engine until the engine stops, or by draining the fuel tank by removing the fuel line at the carburetor or fuel tank. Be careful not to damage the fuel line, fittings, or fuel tank.
2.Drain the carburetor by pressing upward on bowl drain (if equipped) which is located on the bottom of the carburetor bowl. On carburetors without a bowl drain, the carburetor may be drained by loosening the bowl nut on the bottom carburetor one full turn. Allow to completely drain and retighten the bowl nut being careful not to damage the bowl gasket when tightening.
3.If "Gasohol" has been used, complete the above procedure and then put one half pint of unleaded gasoline into the fuel tank and repeat the above procedure. If Gasohol is allowed to remain in the fuel system during storage, the alcohol content can cause rubber gaskets and seals to deteriorate.
Change Oil: If the oil has not been changed recently, this is a good time to do it. See "Oil Change Procedure" on page 3.
Oil Cylinder Bore
1.Disconnect the spark plug wire and ground the spark plug wire to the engine. Remove the spark plug and put a 1/2 ounce (15 ml.) of clean engine oil into spark plug hole.
2.Cover the spark plug hole with a shop towel.
3.Crank the engine over, slowly, several times.
4.Install the spark plug and connect the spark plug wire.
Clean Engine: Remove the blower housing and clean all dirt, grass or debris from the intake screen, head, cylinder cooling fins, carburetor, governor levers and linkage.
4
CHAPTER 2 AIR CLEANERS
GENERAL INFORMATION
The air cleaner is the device used to eliminate dust and dirt from the air supply. Filtered air is necessary to assure that abrasive particles are removed before entering the combustion chamber. Dirt allowed into the engine will quickly wear the internal components and shorten the life of the engine.
Tecumseh engines use either a polyurethane or a
Extremely dirty conditions may require more frequent filter cleaning or replacement.
COVER
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ENTRANCE FROM |
FOAM |
UNDER BLOWER |
ELEMENT |
HOUSING |
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OPERATION
The air cleaner cover allows access to the air filter element(s) and prevents large particles from entering the filter body. Air is filtered through the
In Tecumseh's Kleen Aire® system, air is drawn in through a rotating screen or recoil housing to be centrifugally cleaned by the flywheel before the air enters the air filter.
COMPONENTS
The cover holds the filter element and prevents large debris from entering the filter body.
The polyurethane wrap
The paper or polyurethane filter element is the main filter to trap dust and dirt.
AIR CLEANER BODY
FLOCKED SCREEN
1
COVER
POLYURETHENE
WRAP
PAPER
ELEMENT
AIR CLEANER
BODY
The flocked screen is used as an additional filter on XL or XL/C engine models that use a polyurethane filter element.
2
5
TROUBLESHOOTING OR TESTING
If the engine's performance is unsatisfactory (needs excessive carburetor adjustments, starts smoking abnormally, loses power), the first engine component to be checked is the air filter. A dirt restricted or an oil soaked filter will cause noticeable performance problems. A polyurethane filter may be cleaned following the service procedure listed under "Service" in this chapter. A
SERVICE
Service on the polyurethane filter element (cleaning and oiling) is recommended every three (3) months or every twenty five (25) operating hours, whichever comes first. Extremely dirty or dusty conditions may require daily cleanings.
The paper filter element should be replaced once a year or every 100 operating hours, more often if used in extremely dusty conditions.
NOTE: NEVER RUN THE ENGINE WITHOUT THE COMPLETE AIR CLEANER ASSEMBLY INSTALLED ON THE ENGINE. ALWAYS REPLACE THE FILTER ELEMENT WITH THE PROPER TECUMSEH ORIGINAL REPLACEMENT PART.
DISASSEMBLY PROCEDURE
1.Unlock the tabs or remove the screws or wing nuts holding the air cleaner cover in place.
2.Remove the hex nuts holding the element down if equipped. New nuts are supplied with a new filter and are to be used for proper sealing.
3.Clean the excess contaminants out of the air cleaner body before removing the old element.
4.Remove the old element and the polyurethane
5.On air cleaners that use a flocked screen under the polyurethane element, remove the air cleaner assembly from the carburetor before removing the flocked screen. This prevents dirt from entering the carburetor (diag 3).
6.Clean the inside of the cover and body, remove the old gasket between the carburetor and the air cleaner assembly.
7.Reinstall the air cleaner assembly using a new gasket.
8.Use reverse procedure for reassembly. When installing the polyurethane
WING NUTS
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COVER |
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GASKET |
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FILTER A |
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NUTS |
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(FOAM) |
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FILTER B |
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ENTRANCE |
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BODY |
COVER |
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GASKET |
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FOAM |
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FILTER |
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FLOCKED SCREEN |
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ENTRANCE |
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GASKET3
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This type of air filter or
On the polyurethane filter only,
Clean the air cleaner housing and cover being careful not to allow dirt to fall into the carburetor or intake pipe.
Paper
Paper type air filter elements can only be serviced by replacement. Do not attempt to clean a paper filter element. Replacement filters are available at any authorized Tecumseh Service Outlet. Be sure to use new filter nuts or seals for the air cleaner studs if supplied with the new filter (diag. 5).
Flocked Screen
A flocked screen may be cleaned by blowing compressed air through the screen from the backside. If the screen cannot be cleaned with this procedure, it should be replaced with a new screen.
COVER
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ENTRANCE FROM |
FOAM |
UNDER BLOWER |
ELEMENT |
HOUSING |
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COVER
POLYURETHENE WRAP
PAPER
ELEMENT
AIR CLEANER BODY
AIR CLEANER BODY
FLOCKED SCREEN
4
5
7
CHAPTER 3 CARBURETORS AND FUEL SYSTEMS
GENERAL INFORMATION
Tecumseh overhead valve engines use float type carburetors. Float type carburetors use a hollow float to maintain the operating level of fuel in the carburetor.
The float type carburetor will have a fuel enrichment system of either a primer or a manual choke to provide easy cold engine starting. The carburetor fuel mixtures are either fully adjustable, partially adjustable, or nonadjustable. Carburetor adjustments, cleaning, and related fuel system service is covered in this chapter.
Some Tecumseh engines utilize Walbro carburetors. Basic operation is very similar to the Tecumseh float style carburetor.
Carburetors used by Tecumseh can be identified by a manufacturing number stamping on the carburetor as
illustrated (diag. 1).
When servicing carburetors, use the engine model and specification number to obtain the correct carburetor part number. An alternate method to find the correct carburetor part number is to use the manufacturing number stamped on the carburetor and convert this number to a service part number. In the carburetor section of the Master Parts Manual or Microfiche Catalog, a cross reference chart will convert a carburetor manufacturing number to a Tecumseh Service part number.
Complete carburetor replacement may be accomplished by a standard service carburetor. A standard service carburetor is a basic carburetor that may require the use of original carburetor parts or additional new parts to adapt to the specification. An instruction sheet is provided with the new service carburetor or see “SERVICE” in this chapter.
ALTERNATE LOCATION
FOR MANUFACTURING
NUMBER
89 4F5
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89 |
4F5 |
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MANUFACTURING |
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CARBURETOR |
1 |
NUMBER |
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DATE CODE |
OPERATION
In the “CHOKE” or “START” position, the choke |
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shutter is closed, and the only air entering the engine |
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enters through openings around the shutter. As the |
CHOKE PLATE |
starting device is operated to start the engine, |
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downward piston travel creates a low air pressure area |
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in the engine cylinder above the piston. Higher |
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pressure (atmospheric air) rushes into the engine to |
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fill the created low pressure area. Since the majority |
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of the air passage is blocked by the choke shutter, a |
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relatively small quantity of air enters the carburetor |
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at increased speed. The main nozzle and both idle |
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fuel discharge ports are supplying fuel due to the low |
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air pressure in the intake of the engine. A maximum |
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fuel flow through the carburetor orifices combined with |
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the reduced quantity of air that passes through the |
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carburetor, make a very rich fuel mixture which is |
FLAT |
needed to start a cold engine. |
DOWN |
At engine IDLE speed, a relatively small amount of |
2 |
fuel is required to operate the engine. The throttle is |
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almost completely closed. A fuel / air mixture is supplied through the primary
During INTERMEDIATE engine operation, a second orifice is uncovered as the throttle shutter opens, and more fuel mixture is allowed to atomize with the air flowing into the engine.
During HIGH SPEED engine operation, the throttle shutter is opened. Air flows through the carburetor at high speed. The venturi, which decreases the size of the air passage through the carburetor, further accelerates the air flow. This high speed movement of the air decreases the air pressure at the main nozzle opening. Fuel is forced out the main nozzle opening due the difference in the atmospheric air pressure on the fuel in the carburetor bowl and the reduced air pressure at the main nozzle opening.
8
For the fuel to flow, the carburetor bowl must be either vented externally or internally. Some internally vented float style carburetors use a tygon tube and a vent within the air intake. This tube must be present for the carburetor to operate properly (diag. 3).
Air is bled into the main nozzle through the air bleed located in the air horn. This mixes fuel and air prior to the fuel leaving the main nozzle. Atomization occurs as the fuel mixture contacts the fast moving air stream and the mist flows into the intake of the engine.
TYGON TUBE
INTERNAL VENT
EXTERNAL VENT 3
FUEL PRIMERS
Primers may be mounted remotely or as an integral part of the carburetor. The basic function of the primer is to supply an air pressure charge to the carburetor main well or carburetor bowl to displace fuel directly into the carburetor venturi. This displaced fuel provides a rich mixture necessary for engines to start easily on the first or second attempt (diag. 4 & 5).
Primers must be vented either internally through a passage in the carburetor air horn prior to the venturi or externally through a hole in the primer bulb. The vent allows atmospheric air to enter the fuel bowl during operation and to fill the primer bulb after the primer bulb is released.
PRIMER BULB
VENT
4
PRIMER BULB
MAIN NOZZLE
MAIN JET
5
IMPULSE FUEL PUMPS
Impulse fuel pumps may either be mounted externally onto the carburetor fuel inlet or remotely mounted. This pump is connected in the fuel line between the fuel supply and the carburetor or directly to the fuel inlet.
Impulse fuel pumps are operated by crankcase impulses created by the up and down movement of the piston. A hose called a pulse line connects the fuel pump diaphragm chamber to the crankcase and transmits the impulses to the pump diaphragm. The impulses actuate the diaphragm and flap valves to lift the fuel from the fuel tank to the carburetor (diag. 6). A crankcase overfilled with engine oil can affect pump operation.
FLOAT STYLE CARBURETORS
A float is used to maintain the operating level of fuel in the carburetor bowl. As the fuel is used by the engine, the fuel level in the carburetor bowl drops and the float moves downward. This allows the inlet needle valve to move off the sealing seat. Fuel flows by gravity or a pulse pump into the fuel bowl. As the fuel level in the bowl again rises, it raises the float. This upward float motion moves the inlet needle valve to the closed position. When the needle contacts the seat, the fuel flow is stopped. The tapered end of the inlet needle varies the fuel flow rate and the fuel level in the carburetor bowl remains constant (diag. 7). The float height is set according to the service procedure.
CARBURETOR
FITTING
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VALVE OPEN |
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ATMOSPHERIC |
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VENT |
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FILTER |
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AIR BLEED |
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VALVE OPEN |
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VALVE CLOSED |
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FUEL SUPPLY |
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PULSE LINE |
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TO CRANKCASE |
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êCRANKCASE PRESSURE |
êCRANKCASE SUCTION AND |
á SUCTION FUEL FLOW DIRECTION |
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áATMOSPHERIC PRESSURE ACTING |
FLOW DIRECTION |
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ATMOSPHERIC PRESSURE |
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ON DAMPING DIAPHRAGM |
ATMOSPHERIC PRESSURE |
êCAUSED FUEL FLOW |
6 |
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FUEL FLOW |
ACTING ON DAMPING |
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á DIAPHRAGM |
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IDLE AIR |
MAIN AIR |
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BLEED |
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BLEED |
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CHOKE |
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SHUTTER |
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THROTTLE |
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SHUTTER |
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INLET NEEDLE |
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IDLE |
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AND SEAT |
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ADJUSTMENT |
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FLOAT |
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MAIN NOZZLE |
MAIN |
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ADJUSTMENT |
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9
CARBURETOR VISUAL IDENTIFICATION
Series1 Carburetors
Series 1 carburetors are used on some 4 - 7 model overhead valve engines. This float style carburetor has a smaller venturi than the Series 3 or 4 carburetor and has no bosses on each side of the idle mixture screw. The main and idle mixture may be fixed or adjustable. A remote primer or choke may also be used with this carburetor (diag. 8).
Series 3 & Series 4 Carburetors
Series 3 or 4 carburetors are generally used on 8 through 14 model
To determine whether the carburetor is a Series 3 or Series 4, look at the throttle end of the carburetor. Series 3 will have one throttle plate screw (diag. 10). The Series 4 will have two throttle plate screws (diag. 11).
Series 6 Carburetors
Series 6 carburetors are used on 2 and
Series 7
Series 7 carburetors are totally nonadjustable. The die cast carburetor body is similar in appearance and slightly longer than the Walbro LMK body. The choke shaft is made of a plastic material with an internal slot to hold the choke shutter. The carburetor base is flat to accept a Vector style bowl that is held on with a wire bail. (diag. 13)
9
8
10
11
12
13
10
Series 8
Series 8 carburetors have both a fixed main and a fixed idle circuit. These carburetors are totally nonadjustable. This series of carburetor uses an integral primer system like the Series 6. Distinguish this carburetor from the Series 6 by the fixed idle jet that appears as a screw just above the bowl on the primer side. This fixed idle jet may also be capped. (diag. 14)
CAPPED FIXED
IDLE JET
CAP
14
Series 9
Series 9 carburetors are hybrid versions of the Series 8. This carburetor uses a fixed idle jet and fixed main fuel circuit. This carburetor is totally nonadjustable. The bowl nut uses a ball plug on the bottom to cover the center drilling. Also visible is a plastic main fuel discharge nozzle in the venturi. The Idle mixing well and jet will be visible but not machined (diag. 15)
Series 10
This carburetor is for use on all season engine applications. It is the equivalent of the series "8" with the addition of a choke. It has a fixed main and idle with a serviceable main nozzle and a primer assist, with the added benefit of a choke for cold weather starting.
MIXING WELL
CAST BUT NOT
MACHINED
IDLE JET
CAST BUT NOT
MACHINED
15
CHOKE PLATE
FLAT SIDE DOWN |
15 |
Walbro Model LMK
OHV
Idle mixture screws were adjustable on early production OHV15. This has since changed to a fixed idle jet which may be capped for tamper resistance.
If no spring is visible, the jet is fixed. Servicing should be done by a Authorized Tecumseh Dealer.
LOW IDLE |
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MIXTURE SCREW |
16 |
MAY BE ADJUSTABLE OR FIXED |
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11
TESTING
1.After repeated efforts to start the engine using the procedure listed in the operator’s manual fail, check for spark by removing the high tension lead and removing the spark plug. Install a commercially available spark tester and check for spark. If the spark is bright blue and consistent, proceed to step 2. If no or irregular spark see Chapter 8 under "Testing".
2.Visually inspect the removed spark plug for a wet condition indicating the presence of gasoline in the
cylinder.
NOTE: Check plug for correct reach (diag. 17).
3.If the spark plug is dry, check for restrictions in the fuel system before the carburetor. If the spark plug is wet, continue with step # 7.
CHECK THE FUEL CAP FOR PROPER VENTING. With a proper draining receptacle, remove the fuel line clamp on the carburetor fuel inlet and pull the fuel line off the fitting. Examine the fuel flow with the fuel cap both on and off the fuel tank.
CAUTION: DRAIN THE FUEL INTO AN
STANDARD |
OHV |
PLUG |
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17
APPROVED CONTAINER OUTDOORS, AND AWAY FROM ANY OPEN FLAME OR COMBUSTION SOURCE. BE SURE THE ENGINE IS COOL.
NOTE: Todays fuels can cause many problems in an engines performance, due to the fuels quality and short shelf life. Always check fuel as a primary cause of engine performance.
4.Remove the air filter, heater box, or air cleaner assembly if applicable to visually check that the choke shutter completely closes or check to see if fuel comes out of the main nozzle during priming.
5.If the fuel flow from the tank is adequate and no fuel is evident during priming, the carburetor will need to be removed for service. See “Service” in this chapter or consult the “Carburetion Troubleshooting” chart to diagnose carburetor symptoms. Improper fuel flow indicates the fuel, fuel line, filter or tank require cleaning or replacement.
6.Check the engine compression using a commercially available compression tester and follow the tester’s recommended procedure. Low compression, a dry spark plug, adequate fuel flow, and a known good functional carburetor indicates an internal engine problem exists. See Chapter 9 under “Troubleshooting.”
7.A wet spark plug indicates fuel is being supplied by the carburetor. The engine may be flooded by a restricted air filter, carbon shorted or defective spark plug, excessive choking or over priming, improperly adjusted or defective carburetor. With the spark plug removed and a shop towel over the spark plug hole, turn the engine over slowly 3 or 4 times to remove excess gasoline from the engine cylinder.
CAUTION: KEEP ALL COMBUSTIVE SOURCES AWAY. AVOID THE SPRAY FROM THE SPARK PLUG HOLE WHEN CRANKING THE ENGINE OVER.
8.Replace the air filter if restricted or oil soaked. Replace the spark plug if questionable. Install the spark plug and high tension lead and try to start the engine.
9.If the engine floods and fails to start, the carburetor will require service. See the proceeding “Carburetion Troubleshooting” chart for additional causes. If the carburetor is functioning properly the problem may be ignition timing related. See Chapter 8 “Ignition” under “Troubleshooting.”
SERVICE
Carburetor
Before adjusting any mixture screws the necessary carburetor presets should be made. Check for the proper governor adjustments as outlined in Chapter 4. Identify the correct carburetor model and manufacturer to find locations of the high and low speed adjustment screws. Check the throttle control bracket for proper adjustment allowing a full choke shutter position. See Chapter 4 under "Speed Controls and Linkage". Check to see if the normal maintenance procedures have been performed (oil changed, fresh fuel, air filter replaced or clean). Consult microfiche card #30 to find the correct R.P.M. settings for the engine. Start the engine and allow it to warm to operating temperature. The carburetor can now be adjusted.
NOTE: RPM SETTINGS CAN ALSO BE FOUND ON THE COMPUTERIZED PARTS LOOK UP SYSTEMS.
12
Turn both the main and idle mixture adjusting screws in (clockwise) until finger tight if applicable.
NOTE: OVERTIGHTENING WILL DAMAGE THE TAPERED PORTION OF THE NEEDLE.
Now back the mixture screws out (counterclockwise) to obtain the
NOTE: SOME CARBURETORS HAVE FIXED IDLE AND MAIN JETS. IDENTIFY THE SERIES OF CARBURETOR USING THE VISUAL IDENTI- FICATION IN THIS CHAPTER. IDLE MIXTURE FIXED JETS APPEAR AS ADJUSTING SCREWS WITHOUT TENSION SPRINGS AND ARE NOT ADJUSTABLE.
Final Adjustments
Tecumseh Carburetors
Engine Model |
Main |
Idle |
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carburetors |
1 turn |
1 turn |
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Walbro Carburetors |
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Carburetor Model |
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LMK |
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Fixed |
1 turn if |
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adjustable |
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or seated, |
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if fixed |
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Start the engine and allow it to warm up to normal operating temperature (3 - 5 minutes). Set the speed control to the HIGH or FAST position, then turn the main mixture adjustment screw in (clockwise) slowly until the engine begins to run erratic. Note the position of the screw. Now, turn the screw out (counterclockwise) until the engine begins to run erratic. Turn the screw in (clockwise) midway between these two positions. This will be the best setting.
Set the speed control to the IDLE or SLOW position. Adjust the idle mixture screw following the same procedure used to adjust the main mixture adjustment screw.
Identify the location of both HIGH and LOW speed adjustments, then locate the recommended HIGH and LOW R.P.M. setting according to microfiche card # 30 and adjust the engine speed accordingly.
NOTE: RPM SETTINGS CAN ALSO BE FOUND ON THE COMPUTERIZED PARTS LOOK UP SYSTEMS.
TECUMSEH CARBURETORS
DUAL SYSTEM / SERIES "6" |
SERIES "7" |
SERIES "3" & "4" |
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MAIN |
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IDLE MIXTURE |
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MIXTURE |
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FIXED HIGH AND LOW SPEED |
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PRIMER NO CHOKE |
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MIXTURE |
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WALBRO
CARBURETOR
SERIES "8"
CAPPED
FIXED
IDLE JET
(ADJUSTABLE MAIN FOR
EXPORT)21
SERIES "9"
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SERIES "10" |
22 |
23 |
WALBRO LMK
24
13
If further adjustment is required, the main adjustment should be made under a load condition.
If the engine stops or hesitates while engaging the load (lean), turn the main mixture adjusting screw out (counterclockwise) 1/8 turn at a time, testing each setting with the equipment under load, until this condition is corrected. A few Tecumseh carburetors were built as air adjust idle system. If you have one, the adjustments are reversed out for lean in for richer.
If the engine smokes excessively (rich), turn the main adjusting screw in (clockwise) 1/8 turn at a time, testing each setting with the equipment under load, until this condition is corrected.
After the main mixture screw is set, move the speed control to the IDLE or SLOW position. If the engine does not idle smoothly, turn the idle mixture screw 1/8 turn either in (clockwise) or out (counterclockwise) until engine idles smoothly.
Recheck the high and low R.P.M. setting and adjust as necessary.
CARBURETOR DISASSEMBLY PROCEDURE
NOTE : CARBURETORS THAT ARE EMISSION COMPLIANT (MANUFACTURING NUMBERS 5000 OR GREATER) WITH FIXED IDLE OR MAIN JETS ARE TO BE REMOVED BY DEALERS ONLY FOR INSPECTION AND CLEANING.
1.Note or mark the high and low mixture adjusting screws to aid in reassembly (if applicable). Remove the high speed mixture screw, bowl nut, and float bowl. Remove the idle mixture screw assembly. On Series 7 carburetors, release the wire retainer that retains the bowl and remove the bowl assembly. If a screwdriver or similar tool is used to release the retainer, carefully move the retainer to prevent bending of the wire.
2.Series 8 carburetors have a tamper resistant cap, over the fixed idle jet. (diag. 21). The cap is removed by piercing it with an ice pick or similar instrument, then remove the jet for service, always replace the cap.
3.Note the position of the spring clip on the inlet needle and float. Remove the float hinge pin with a needlenose pliers. Some carburetors use a float dampening spring to aid the inlet valve to maintain a steady position in rough service applications. Note the position of the hooks before removing the float hinge pin (diag. 25). On Series 7 carburetors, grasp the crossbrace on the float with a needlenose pliers and pull straight out to release the float hinge pin.
4.Remove the float, clip, and inlet needle.
5.Remove the inlet needle seat using a wire or a paper clip with a 3/32" (2.38 mm) hook end (Tecumseh carburetors only, Walbro model LMK uses a
6.On Series 7 only, remove the main nozzle tube, "O" ring, and spring located in the center leg of the carburetor bowl. Remove the bowl drain screw and gasket. Remove the spring, metering jet, and "O" ring.
7.Note or mark the action of the choke and throttle shutters and the hook points of the choke or throttle return spring or seal retainer springs located on the top of the choke or throttle shaft.
NOTE: MARK THE EDGES OF THE THROTTLE AND CHOKE SHUTTERS PRIOR TO DISASSEMBLY. THE SHUTTERS HAVE BEVELED EDGES AND MUST BE INSTALLED IN THE ORIGINAL POSITION.
Remove the throttle shutter, throttle shaft, choke shutter, springs and choke shaft by removing the screw or screws that attach the throttle or choke shutter to the shaft inside the air horn. To remove the choke shaft assembly on Series 7 or Walbro LMK carburetors, grasp the choke shutter with a pliers and pull it through the slot in the choke shaft. Slide the choke shaft out of the carburetor body.
LONG END |
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CLIP |
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OPEN END |
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OF CLIP |
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END |
CHOKE |
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3/32" (2.38 mm)
26
27
14
8. Remove the primer bulb (if equipped) by |
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grasping with a pliers and pulling and twisting |
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carburetor. Secure the carburetor in a vise |
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equipped with protective jaws. Use a small |
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chisel sharpened to a 1/8" (3.175 mm) wide |
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wedge point. Drive the chisel into the plug to |
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pierce the metal and push down on the chisel |
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28 |
to pry the plug out of the hole (diag. 29). |
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10.Note the direction of the inlet fitting. If necessary the inlet fitting can be removed by pulling with a pliers or vise, do not twist. The fitting must be replaced. Tap a
11.The Walbro LMK carburetor main fuel jet can be removed only if the jet is damaged or if a high altitude jet is needed to be installed. To remove place the carburetor firmly in a soft jawed vice. Using a punch the same size or slightly smaller than the jet, drive the jet through and into the center leg. Insert the high altitude jet in the same hole. Using a punch slightly larger than the diameter of the new jet, tap it into place flush with the outside of the center leg casting (diag. 31).
SMALL |
PIERCE PLUG |
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PRY OUT |
WITH TIP |
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CHISEL POINT |
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DO NOT REMOVE PLUGS
BRASS OR BALL PLUG
BALL PLUG IDLE FUEL PASSAGE REDUCTION ROD INSIDE 30
WALBRO LMK SERIES ATMOSPHERIC
VENT
HIGH SPEED JET |
31 |
Impulse Fuel Pump
The valve type impulse pump can be serviced using the following procedure.
1.Remove the old filter on the back of the pump body if applicable.
2.Note or mark the pump body alignment, remove the four screws and disassemble the pump.
3.Remove the gaskets, diaphragms, old valves and spring bearing from the spring.
4.Clean the body parts with solvent.
5.Install new valves with the face of the valve facing the raised portion of the passage. After installation, cut off the extended portion of the valves.
6.Install the diaphragms against the center portion of the body with the gaskets against the outside covers. The parts can only can be assembled one way without damage.
7.Install the spring bearing on the new spring and place into position.
8.Assemble the body sections, install the retaining screws, and torque the screws to 12 - 16 inch pounds (1.36 - 1.81 Nm).
9.Install new filter in pump cavity if applicable.
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10 - *Spring, Pressure |
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11 - *Filter, Air |
32 |
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FLOAT ADJUSTING PROCEDURE
All Tecumseh carburetors with an adjustable float require the correct float height to achieve the proper operation and easy engine starts. To check the float setting, hold the carburetor in an upside down position. Remove the bowl nut, float bowl, and "O" ring. Place an 11/64" (4.36mm) diameter drill bit across the top of the carburetor casting on the opposite side and parallel to the float hinge pin. The float must just touch the drill bit when the bit is flush with the edge of the float. If the float is too high or too low, adjust the height by bending the tab accordingly. If the required adjustment is minor, the tab adjustment may be made without removing the float and carefully inserting a small bladed screwdriver to bend the tab.
FLOAT
FLOAT HINGE
AND AXLE
FLOAT
SETTING
11 / 64" (4.36 mm)
ADJUSTING TAB |
INLET NEEDLE |
33 |
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AND SEAT |
If float sticking occurs due to deposits, or when the fuel tank is filled for the first time, this condition can be quickly corrected by loosening the carburetor bowl nut one full turn. Turn the bowl 1/4 inch in either direction, then return the bowl to its original position and tighten the bowl nut.
THE TECUMSEH SERIES 7 AND THE WALBRO MODEL LMK CARBURETOR HAVE A FIXED AND NONADJUSTABLE FLOAT HEIGHT.
Inspection
After careful disassembly of the carburetor and the removal of all non metallic parts, all metallic parts should be cleaned with solvent, or commercial carburetor cleaner, no longer than 30 minutes. Wearing eye protection, use compressed air and soft tag wire or monofilament fishing line to clean internal carburetor passages. To perform a proper carburetor rebuild, the welch plugs must be removed to expose the drilled passages.
Throttle and Choke
Examine the throttle and choke shaft, and carburetor body at the bearing points and holes into which the linkage is fastened, and replace if worn or damaged. Any excessive wear in these areas can cause dirt to enter the engine and cause premature wear. If dust seals are present, check the seal condition and the correct placement next to the carburetor body.
Idle and High Speed Mixture Adjusting Screw
Examine the idle mixture needle tip and tapered surface for damage. The tip and tapered surface of the needle must not show any wear or damage. If either is worn or damaged, replace the adjusting needle. Tension is maintained on the screw with a coil spring. Replace the “O” ring seal if removed (diag. 34).
Examine the tapered surface of the high speed mixture needle. If the tapered surface is damaged or shows wear, replace the needle.
"O" RING
RETAINER NUT
BRASS WASHER
SPRING
HIGH SPEED
ADJUSTMENT
SCREW
34
Fuel Bowl Retaining Nut
The bowl nut contains the passage through which fuel is delivered to the high speed and idle fuel system of the carburetor. If a problem occurs with the idle system of the carburetor, examine the small fuel passage in the annular groove in the bowl nut. This passage must be clean for the proper transfer of fuel into the idle metering system.
Bowl nuts that are used on adjustable main, float style carburetors may use either one or two metering ports. This difference relates to calibration changes of the carburetor, depending on the application (diag. 35).
NOTE: DO NOT INTERCHANGE BOWL NUTS.
The fuel inlet ports must be free of any debris to allow proper fuel flow.
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IDLE FUEL |
FUEL- |
FUEL- |
TRANSFER |
INLET |
METERING |
PASSAGE |
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16
Fuel Bowl, Float, Needle and Seat
NOTE: To prevent damage to the float bowl on Series 7 carburetor, pull straight up with a needle nose pliers in the pocket closest to the main fuel well (diag. 37).
The float bowl must be free of dirt and corrosion. Clean the bowl with solvent or carburetor cleaner (soak 30 minutes or less).
Examine the float for cracks or leaks. Check the float hinge bearing surfaces for wear, as well as the tab that contacts the inlet needle. Replace any damaged or worn parts.
The needle and seat should be replaced if any fuel delivery problems are experienced (flooding or starvation). Sealing problems with the inlet needle seat may not be visible and replacement is recommended. Only the inlet needle is serviceable on the Walbro model LMK carburetor.
FLOAT HINGE |
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SEAT |
MAIN NOZZLE |
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SEAT |
EMULSION |
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RETAINING |
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GROOVE |
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JET/BOWL NUT |
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BOWL RETAINER |
BOWL DRAIN |
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38 |
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36 |
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37 |
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SERIES 8, 9 & 10 |
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SERIES 7 |
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CHOKE SHAFT |
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THROTTLE SHAFT & LEVER |
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THROTTLE SHAFT |
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THROTTLE RETURN SPRING |
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THROTTLE SHUTTER |
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THROTTLE DUST SEAL |
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DUST SEAL WASHER |
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CHOKE DUST |
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DUST SEAL |
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SEAL |
THROTTLE RETURN SPRING |
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THROTTLE |
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FUEL FITTING |
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IDLE SPEED SCREW |
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CHOKE RETURN |
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SHUTTER |
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SPRING |
WELCH PLUG |
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SCREW |
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PRIMER BULB/ |
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CHOKE |
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IDLE MIXTURE |
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RETAINER |
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SHUTTER |
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SCREW |
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RING |
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TENSION SPRING |
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THROTTLE SHUTTER |
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"O" RING |
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FUEL FITTING |
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PRIMER BULB |
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&nbsnbsp; |
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SCREW |
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FILTER |
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SEAT AND CLIP INLET |
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INLET NEEDLE |
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ATMOSPHERIC VENT |
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NEEDLE |
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SPRING CLIP |
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FLOAT |
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FLOAT SHAFT |
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WELCH PLUG |
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FLOAT SHAFT |
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FLOAT |
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"O" RING |
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FLOAT BOWL |
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FLOAT BOWL |
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BOWL NUT WASHER |
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BOWL NUT WASHER |
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HIGH SPEED BOWL NUT |
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BOWL NUT |
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WALBRO LMK |
39 |
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SERIES 6 |
40 |
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17
ASSEMBLY PROCEDURE
Welch Plugs
To install a new welch plug after cleaning the carburetor, secure the carburetor in a vise equipped with protective jaws. Place the welch plug into the receptacle with the raised portion up. With a punch equal to the size of the plug hole, merely flatten the plug. Do not dent or drive the center of the plug below the top surface of the carburetor. After installation of the welch plug, seal the outer diameter with fingernail polish (diag. 41).
NEW WELCH PLUG |
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FLAT END PUNCH |
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SAME OR |
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LARGER |
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DIAMETER OF |
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PLUG HOLE |
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41 |
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Throttle Shaft and Plate |
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When reassembling Tecumseh or Walbro carburetors, |
THROTTLE |
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THROTTLE |
PLATE |
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LEVER |
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it is important that the lines, lettering, or numbers on |
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TWELVE |
the throttle plate are facing out when in the closed |
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O'CLOCK |
position. If the throttle plate has only one line, this |
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POSITION |
line should be positioned in the 3 o’clock position on |
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Series 3, 4, and 7 carburetors, and at the 12 o'clock |
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position on Series 1, 6, 8, 9 carburetors. (diag. 42 & |
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43). |
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42 |
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Test the operation of the throttle and return spring if |
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equipped. If binding occurs, correct by loosening the |
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THREE |
screws and repositioning throttle plate. |
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O'CLOCK |
Always use a new screw(s) when reinstalling the |
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POSITION |
throttle shutter to prevent the screws from loosening |
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and being drawn into the engine. New Tecumseh |
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screws are treated with |
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them in place. |
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NOTE: NEVER REUSE OLD SCREWS. |
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43 |
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On Walbro LMK and Series 7 carburetors, install the |
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DUST SEALS |
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throttle return spring on the throttle shaft with the |
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squared end up. Slide the foam dust seal over the |
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spring. Insert the throttle lever assembly into the |
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carburetor body with both tangs of the return spring |
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on the left side of the center boss (viewed from throttle |
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end) and the flat side of the shaft toward the carburetor |
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mounting flange. Install the throttle shutter to the |
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throttle shaft using notes or marks to place the shutter |
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as originally found (Series 7 must have the line on the |
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shutter at the 3 o'clock position) (diag. 44). |
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Always use new throttle shutter screws when |
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44 |
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reinstalling. Install the screws so they are slightly |
SERIES 7 |
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loose. Apply light downward pressure on the throttle |
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shaft and rotate it clockwise to seat the throttle shutter |
THROTTLE LEVER |
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in the bore, then tighten the throttle shutter screws. |
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Check for binding by rotating the throttle shaft. If |
THROTTLE PLATE |
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necessary, adjust the throttle shutter by loosening and |
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repositioning the shutter, then retighten the screws |
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(diag. 45). |
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WALBRO LMK SERIES |
45 |
18
Choke Shaft and Plate |
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The choke plate is inserted into the air horn of the |
CHOKE PLATE |
carburetor in such a position that the flat surface (if |
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applicable) of the choke is down. Choke plates will |
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operate in either direction. Make sure it is assembled |
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properly for the engine. Test the operation of the choke |
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and return spring function if equipped (diag. 46). |
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Always use a new screw(s) when reinstalling the |
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choke shutter as the screws are treated with |
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adhesive to secure them in place. |
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FLAT DOWN |
46 |
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NOTE: NEVER REUSE OLD SCREWS. |
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The choke shaft and plate must be in the closed |
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SPRING |
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HOOKUPS |
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position prior to tightening the screws. Hard starting |
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may be due to insufficient choking action because of |
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a misaligned choke plate. Correct by readjusting the |
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choke plate to close completely. Note the cutout |
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position of choke shutter if applicable. |
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On Walbro LMK and Series 7 carburetors, install the |
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choke return spring on the choke shaft with the |
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squared end up and hooked into the notch in the plate. |
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Work the dust shield up around the spring and insert |
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47 |
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the choke shaft into the carburetor body. Rotate the |
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shaft counterclockwise until the tang on the spring |
PRESS IN PARTIALLY |
SOME INLET FITTINGS |
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rests against the left side of the center boss on the |
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THEN APPLY |
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carburetor body (viewed from choke end) . Rotate the |
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LOCTITE |
STRAINER |
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choke shaft approximately 1/4 turn counterclockwise |
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and insert the choke shutter into the slot in the choke |
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shaft. Make sure the tabs on the shutter lock the choke |
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shaft between them. Rotate the shaft and check for |
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binding, the choke must return to the open position |
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when released (diag. 47). |
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Fuel Inlet Fitting |
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48 |
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When installing the fitting, insert the tip into the |
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carburetor body. Support the carburetor body with a |
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wood block to avoid damage to other parts. Use a |
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RETAINER NUT |
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"O" RING |
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bench vise or press to install the fitting squarely. Press |
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BRASS WASHER |
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it in until it bottoms out (diag. 48). |
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SPRING |
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High and Low Speed Adjusting Screw, Main |
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Nozzle |
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HIGH SPEED |
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When reassembling, position the coil spring on the |
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ADJUSTMENT |
49 |
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SCREW |
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adjusting screws, followed by the small brass washer |
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and the “O” ring seal. Turn the high speed adjustment |
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screw into the bowl nut and the low speed mixture |
FLOAT HINGE PIN |
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screw into the carburetor body (diag. 49). |
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Some carburetors may have a fixed main mixture or |
NEEDLE & |
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FLOAT |
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both a fixed idle mixture and main mixture, and are |
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SEAT |
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not adjustable. |
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On Series 7carburetors, place the main nozzle spring |
SEAT RETAINING |
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MAIN NOZZLE EMULSION |
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into the main nozzle cavity. Apply oil to the main nozzle |
RING |
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"O" RING POSITIONED IN |
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"O" ring and push the main nozzle into the cavity |
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GROOVE |
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with the "O" ring end in first. |
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SPRING |
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Next install the "O" ring in the main jet cavity. Place |
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IDLE RESTRICTION |
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the spring over the shoulder on the main jet and push |
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BOWL |
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the jet into the cavity with the main jet toward the "O" |
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ring. Place a new gasket on the drain screw and |
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"O" RING |
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tighten in position (diag. 50). |
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MAIN JET |
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||
On Walbro LMK carburetors, the main jet can be |
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MAIN JET SPRING |
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GASKET |
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replaced by pressing it into the center leg of the |
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BOWL |
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carburetor until flush. (diag. 31 page 15). |
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DRAIN |
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NOTE: FOR HIGH ALTITUDE JETTING, CONSULT |
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BOWL RETAINER |
50 |
|||||
BULLETIN 110. |
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19
Inlet Needle and Seat
Make sure the seat cavity is clean. Moisten the seat with oil and insert the seat with the grooved side down and away from the inlet needle. Press the seat into the cavity using a 5/32" (3.969 mm) flat punch, making sure it is firmly seated (diag. 51). On Series "7" carburetors, install the seat retainer into the cavity and push it down using the flat punch until it contacts the seat.
PUSH IN UNTIL SEAT RESTS ON BODY SHOULDER
IF YOUR CARBURETOR HAS A STEEL SEAT RETAINING RING
INLET NEEDLE
SEATS AT THIS
POINT
5/32" (3.969 mm)
FLAT PUNCH
SEAT
INSERT THIS
FACE FIRST
51
The inlet needle hooks onto the float tab by means of a spring clip. To prevent binding, the long, straight end of the clip should face the choke or air filter end of the carburetor as shown (diag. 52).
LONG END |
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CLIP |
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||
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OPEN END OF CLIP |
|
OF CLIP |
|
||||
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|
||||
Points toward choke |
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|
|||
end |
|
THROTTLE |
|||
|
|
|
|
|
|
|
|
|
|
|
END |
CHOKE |
|
|
|||
END |
52 |
||||
|
|
|
|
||
Float Installation
On Series 7 carburetors, slide the hinge pin into the hinge on the float. Position the needle into the fuel inlet and snap the float pin into the tabs on the float bowl. Float height is not adjustable.
On Series 7 carburetors and the Walbro LMK, reinstall the inlet needle on to the float and place it into the carburetor (diag. 53).
1.When rebuilding a carburetor with a clip on the needle, position carburetor float side up for assembly.
2.Place the inlet needle and spring clip onto the float as shown. The long end of the spring clip must point towards the choke end of the carburetor. This will ensure that the inlet needle will move up and down in a straight line (diag. 53).
3.To set the proper float height on carburetors except Series 7 and Walbro LMK, see adjusting procedure.
4.Some Tecumseh float style carburetors have a damper spring which is installed as shown in diag. 55.
SERIES 7 WALBRO / LMK |
53 |
|
|
|
CLIP |
|
OPEN END |
|
OF CLIP |
LONG END |
|
OF CLIP |
|
Points toward choke end |
54 |
|
|
|
|
POINTS TOWARD |
|
THE CHOKE END |
|
55
20
Fuel Bowl And Bowl Nut
Whenever a carburetor bowl is removed for service, the fuel bowl “O” ring (or gasket on Series "7") and the bowl nut washer must be replaced. For easier installation, lubricate the “O” ring with a small amount oil.
Installing the Float Bowl
Install the float bowl by placing the detent portion opposite of the hinge pin. Make sure the deepest end of the bowl is opposite of the inlet needle. The bowl has a small dimple located in the deepest part. The purpose of this dimple is to minimize the chances of the float sticking to the bottom of the bowl caused by stale fuel.
Impulse Fuel Pump
The diaphragms must be installed against the center body with the gaskets against the outside covers. The parts are designed so they cannot be misassembled without damage (diag. 57).
To test the unit, assemble the carburetor to the engine, leaving the fuel line from the pump off. Use a different fuel tank remotely placed above the carburetor to provide gravity fuel flow to the carburetor inlet to run the engine while testing the pump. Make sure fuel is available in both fuel tanks and the original fuel tank's fuel line is connected to the fuel pump inlet. Place the pump outlet line in a proper draining receptacle. With the pulse line connected from the engine crankcase to the pump and the engine running, a definite fuel flow should result at the pump outlet.
If the flow is erratic or intermittent, the pump needs repair or replacement.
To install, start the retainer and bulb into the casting with the retainer tabs pointed out. Firmly push the bulb and retainer into position using a 3/4'’ (19.05 mm) deep well socket (diag. 58).
Final Checks
Before reinstalling a newly overhauled carburetor, pre- set the main mixture adjustment screw, the idle mixture adjustment screw and the idle speed adjustment screw. See
DETENT
56
CARBURETOR
FITTING
VALVE CLOSED |
VALVE OPEN |
|
|
ATMOSPHERIC |
|
|
DIAPHRAGM |
|
|
VENT |
|
|
|
|
|
|
FILTER |
|
|
AIR BLEED |
VALVE OPEN |
VALVE CLOSED |
|
|
||
FUEL SUPPLY |
PULSE LINE |
|
|
|
TO CRANKCASE |
êCRANKCASE PRESSURE |
êCRANKCASE SUCTION AND |
á SUCTION FUEL FLOW DIRECTION |
áATMOSPHERIC PRESSURE ACTING |
FLOW DIRECTION |
ATMOSPHERIC PRESSURE |
ON DAMPING DIAPHRAGM |
ATMOSPHERIC PRESSURE |
êCAUSED FUEL FLOW |
áFUEL FLOW |
á ACTING ON DAMPING |
|
|
DIAPHRAGM |
|
|
|
57 |
58
21
CHAPTER 4 GOVERNORS AND LINKAGE
GENERAL INFORMATION
Tecumseh 4 cycle engines are equipped with mechanical type governors. The governor’s function is to maintain a R.P.M. setting when engine loads are added or taken away. Mechanical type governors are driven off the engine’s camshaft gear. The governor follower arm rests on the center of the governor spool on center force governors, and off to one side on other governor systems. Changes in engine R.P.M. cause the governor lever to move the solid link that is connected from the governor lever to the throttle in the carburetor. The throttle is opened when the engine R.P.M. drops and is closed as an engine load is removed.
This chapter includes governor assembly linkage illustrations to aid in governor or speed control assembly.
OPERATION
As the speed of an engine increases, the governor weights on the governor gear move outward by centrifugal force. The shape of the governor weights force the governor spool to lift. The governor rod maintains contact with the governor spool due to the governor spring tension. The governor rod rotates causing the attached outer governor lever to push the solid link and close the throttle opening. When the
THROTTLE
SPRING
GOVERNOR SHAFT
engine speed decreases, the lower centrifugal force allows the governor weights to be pulled in by the governor spring. The governor rod rotates and the solid link moves the throttle to a more open position (diag. 1).
WEIGHTSGOVERNOR SPOOL
GOVERNOR GEAR
1
TROUBLESHOOTING
Engine operation problems where the governor is suspected to be the cause may actually be the result of other engine system failures. Hunting (engine R.P.M. surging up and down) indicates that the engine is incapable of maintaining a constant R.P.M. with or without an engine load. Engine overspeeding must be corrected immediately before serious engine damage occurs. Use the applicable following procedure to diagnose a suspected governor failure.
ENGINE OVERSPEEDING
1.If the engine runs wide open (faster than normal), shut the engine off or slow it down immediately.
2.Check the condition of the external governor shaft, linkage, governor spring, and speed control assembly for breakage or binding. Correct or replace binding or damaged parts.
3.Follow the governor adjustment procedure and reset the governor - see "Service" in this chapter.
4.Run the engine. Be ready to shut the engine off if an overspeed problem still exists. If the problem persists, the engine will require disassembly to inspect the governor gear assembly for damage, binding, or wear.
5.See Chapter 9 under "Disassembly Procedure" to disassemble the engine.
6.Remove the governor gear assembly. Repair or replace as necessary.
ENGINE SURGING
1.Try to stabilize the engine R.P.M. by holding in one position the solid link between the governor arm and the carburetor throttle, using a pliers or fingers.
2.If the engine R.P.M. stabilizes, the governor or governor adjustment should be checked. See "Service" governor adjustment procedure in this chapter. If the engine R.P.M. does not stabilize, the engine will require additional checks see Chapter 9 under "Troubleshooting".
3.If the problem persists after the governor adjustment, check the engine R.P.M. found on microfiche card # 30. The R.P.M. settings are critical. If the R.P.M. setting for high and low speed are within specification and a slight surge is experienced, increasing the engine idle R.P.M. setting slightly may eliminate this condition.
4.Check the governor shaft or linkages for binding, wear, or improper hookup. Check the governor spring for adequate tension or damaged condition. Repair or replace as necessary.
22
SERVICE
GOVERNOR ADJUSTMENT
With the engine stopped, loosen the screw holding the governor lever to the governor shaft clamp. Push the governor lever to move the carburetor throttle plate to the wide open position. Rotate the governor clamp counterclockwise on all overhead valve engines covered in this manual. Hold the lever and clamp in this position while tightening the screw (diag. 2).
PUSH
LEVER TO
WIDE OPEN
THROTTLE
Ý
GOVERNOR
CLAMP
SCREW
Ú
TURN CLIP COUNTERCLOCKWISE ON ALL VERTICAL |
|
SHAFT ENGINES EXCEPT VLV & VLXL. CLOCKWISE |
|
ON ALL HORIZONTAL SHAFT ENGINES EXCEPT |
|
OHH,OHSK 50,55 & OHM, OHSK 110,120. |
2 |
|
THROTTLE LINK |
THROTTLE PLATE |
THROTTLE OPEN |
|
|
|
(PUSH COUNTERCLOCKWISE) |
|
GOVERNOR |
|
STANDARD |
|
|
LOCATION |
|
|
LEVER |
THROTTLE OPEN |
|
|
|
|
||
|
(PUSH COUNTER- |
GOVERNOR |
|
|
CLOCKWISE) |
|
|
GOVERNOR |
|
LEVER |
|
|
|
|
|
ROD |
|
GOVERNOR |
|
GOVERNOR |
|
SCREW |
|
|
|
|
|
CLAMP |
|
GOVERNOR |
|
SCREW |
|
ROD |
|
|
|
|
|
YOU MUST USE THIS |
|
GOVERNOR |
|
LINK POSITION |
|
CLAMP |
|
|
|
|
|
ROTATE LEVER |
|
ROTATE CLAMP |
|
& ROD |
THROTTLE |
COUNTERCLOCKWISE |
|
COUNTER- |
|
|
|
CLOCKWISE |
PLATE |
|
|
|
(TOP VIEW) |
|
3 |
OHH SERIES - NEW STYLE |
OHH SERIES - OLD STYLE |
||
GOVERNOR GEAR AND SHAFT SERVICE
After the cylinder cover is removed from the engine, the governor spool, gear, or governor shaft can be removed. On some governor assemblies, the retaining ring must be removed to allow the spool or gear to slide off the shaft. Other governor shafts use an upset to hold the governor spool on. If the gear requires replacement, the governor shaft will have to be removed.
Governor Gear or Shaft Replacement, Upset Style Governor Shaft
1.Grip the original spool in a vise and use a twisting and pulling motion on the flange until the spool is free.
2.Clamp the shaft in a vise and pound gently on the flange with a wooden or plastic mallet to remove the shaft (diag. 4).
NOTE: DO NOT TWIST THE SHAFT WHEN REMOVING. THE SHAFT BOSS MAY BECOME ENLARGED AND THE PRESS FIT WILL NOT SECURE THE NEW GOVERNOR SHAFT.
3.To install a new shaft, first assemble the gear and washer on the shaft. Start the shaft into the hole with a few taps from a soft faced hammer.
4.Place the flange in a press with a solid piece supporting the area below the shaft boss. Press the shaft in until a part # 670297 (.0125" / .3175 mm) shim just becomes snug (.010"
4
GEAR
SHIM
WASHER
SHAFT BOSS
5
670297 (modified)
23
Governor Shaft Replacement, Retaining Ring Style
1.Remove the retaining ring, spool, gear assembly, and washer(s).
2.Clamp the shaft in a vise and pound gently on the flange with a wooden or plastic mallet to remove the shaft.
NOTE: DO NOT TWIST THE GOVERNOR SHAFT WHEN REMOVING. THE SHAFT BOSS MAY BECOME ENLARGED AND THE PRESS FIT WILL NOT SECURE THE NEW GOVERNOR SHAFT.
3.Start the new shaft into the shaft boss by tapping with a soft faced hammer.
4.Refer to the chart at right for the proper shaft exposed length from the mounting surface. Add a drop of red Loctite 271 and press the governor shaft to the proper depth using a press or a vise. Wipe the extra Loctite off after installation.
5.Reassemble the washer (s), governor gear, and spool followed by the retaining ring.
ENGINE MODEL |
EXPOSED SHAFT LENGTH |
1.319" - 1.334" |
|
OVRM |
(33.502 - 33.883 mm) |
|
|
OHM |
1.085" - 1.100" |
(27.559 - 27.940 mm) |
|
OVM |
|
OVXL |
1.350" - 1.365" |
OHV |
|
|
|
RETAINING
RING
SPOOL
RETAINING
RING
GEAR ASSY. |
|
|
(GOV.) |
WASHER |
|
SHAFT |
|
OVRM TYPE I |
7 |
SERVICED AS ASSEMBLY
SPOOL
UPSET
SHAFT
GEAR ASSY.
(GOV.)
WASHER
OVRM TYPE II |
8 |
RETAINING
RING
SPOOL
WASHER
RETAINING
RING
GEAR ASSY.
(GOV.)
WASHER
SPACER
SHAFT
MEDIUM FRAME 9
SPOOL
SHAFT
GEAR ASSY. (GOV.)
WASHER
OHH /
SPOOL
WASHER
RETAINING
RING
GEAR ASSY. (GOV.)
WASHER
SPACER
NOTE; SPACER
MAY BE PART
OF THE GEAR
ASSEMBLY.
SHAFT
OVM / OHV / OHM
24
Speed Controls And Linkage
Many different types of speed controls and linkage are used for O.E.M. applications. Linkage attachment points are best recorded or marked prior to disassembly. This assures the correct placement during reassembly. The solid link is always connected from the outermost hole in the governor lever to the throttle in the carburetor. The governor spring is connected between the speed control lever and the governor lever. Vertical shaft engines may use an adjustable intake pipe mounted speed control bracket located above the carburetor, or a vertical or horizontal control mounted on the side of the engine. The ignition ground out terminal, idle R.P.M. and high speed R.P.M. adjustment screws may be located on the speed control bracket.
The adjustable speed control bracket which is mounted on the intake pipe must be aligned properly when installing. To align the control bracket, use the following steps.
1.Loosen the two screws on the top of the panel.
2.Move the control lever to full wide open throttle position and install a wire or aligning pin through the hole in the top of the panel, the hole in the choke actuating lever, and the hole in the choke (diag. 12).
3.With the components aligned, tighten the two screws on the control panel.
The following pages show common linkage hookup arrangements. Whenever the carburetor or the governor linkage is removed or replaced, the engine R.P.M.'s should also be checked. Use microfiche card #30 or contact a local Tecumseh dealer for the correct R.P.M. settings for the engine model and specification.
NOTE: RPM SETTINGS CAN ALSO BE FOUND ON THE COMPUTERIZED PARTS LOOK UP SYSTEMS.
OHH REMOTE SPEED CONTROL
The engine and equipment control must be adjusted to allow the engine control lever to touch the high speed stop when the equipment control is set in the "highspeed" or "fast" position. Loosen the bowden wire clamp, place the equipment control to the "fast" position, move the engine control lever to contact the high speed stop, and hold the lever in this position while tightening the bowden wire clamp.
12
HIGH SPEED STOP
13
OHH GOVERNED IDLE SPEED CONTROL
This control is adjusted by bending the tabs on the control bracket to achieve the correct idle speed and high speed. When the engine is running, the governor controls both the idle and the high engine speed. In order for the governor to respond properly to a crankshaft load at engine idle, the idle speed screw on the top of the carburetor must be set 600 RPM lower than the governed idle speed. Use the following procedure to set the engine speeds (diag. 14 & 16).
1.Check to find the correct engine speeds found on microfiche card # 30 or using the Computer Parts Look- up System.
2.Start and allow the engine to run (
3.Allow the governor to control the throttle. Use a
4.Slide the control knob to the high speed position and bend the tab as shown to achieve the specified
governed high engine speed.
25
NOTE: Early production OHH engines did not have governed idle, set only the idle crack screw and high speed governor stop.
|
WINTER |
|
|
APPLICATION |
|
|
CONTROL |
|
|
GOVERNED |
|
|
IDLE LINK |
|
|
AND |
|
|
ADJUSTMENT |
|
HIGH SPEED |
|
|
ADJUSTMENT |
BEND TO ADJUST SPEED |
|
|
|
|
|
DECREASE ÞÞ INCREASE |
14 |
OHH REMOTE & MANUAL |
||
GOVERNOR SPRING |
GOVERNED IDLE LINK |
|
OHH RV CONTROL |
16 |
THROTTLE CRACK SCREW |
||
|
|
GOVERNED |
|
|
HIGH SPEED |
|
|
ADJUST |
GOVERNED IDLE SCREW |
|
|
OHSK / OHM CONTROL |
18 |
|
NOTE: ON REMOTE |
HIGH SPEED ADJUST |
CONTROL THIS |
LOW SPEED ADJUST |
WILL NOT |
|
BE PRESENT |
|
HIGH SPEED ADJUST |
|
OHH FIXED SPEED |
|
15 |
THROTTLE CRACK SCREW |
|||
|
|
|
GOVERNED |
|
|
|
HIGH SPEED |
|
|
|
ADJUST |
|
BEND |
|
|
CORRECT BUSHING |
INCREASE ÞÞ DECREASE |
|
|
|
|
|
|
INSTALLATION DEEP |
|
|
|
SIDE |
GOVERNED IDLE TAB |
|
|
HERE |
|
|
|
|
|
|
|
|
OH / OHSK CONTROL |
17 |
|
LOW SPEED TAB |
HIGH SPEED TAB |
HIGH SPEED
PIN POSITION
Þ |
|
DECREASE |
|
Þ |
|
INCREASE |
|
OVRM SNAP IN CONTROL |
19 |
OVRM20
OVRM21
26
HIGH
SPEED
ADJUST
GOVERNED IDLE
ADJUST
OVM / OVXL GOVERNOR OVERRIDE 22
OHV11 - 17 SPEED CONTROL |
23 |
|
|
|
|
SPEED CONTROL BRACKET |
DETENT BEARING PLATE |
CONDUIT CLIP |
|
BUSHING |
|
|
LOCK NUT |
SCREW |
CONTROL KNOB |
|
||
|
|
GROUNDING TERMINAL
ADDITION BOWDEN WIRE BRACKET
WAVE WASHER
CONTROL LEVER |
|
|
WASHER |
|
|
NOTE: THIS CONTROL IS STANDARD ON SERVICE ENGINES AND IS OPTIONAL TO CUSTOMERS |
24 |
|
CONVERSION TO REMOTE CONTROL
Remove the manual control knob by squeezing together with a pliers or prying with a screw driver. Remove the air cleaner cover and air cleaner element to gain easier access to the speed control lock nut that holds the control levers together.
Remove the 3/8" (9.525 mm) locknut, bushing, wave washer, control lever, and the detent bearing plate.
Reassembly of REMOTE control.
Discard the detent bearing plate and in its place install the washer with the smaller I.D. from the new parts bag. Install the lever over the post making sure that the end of the lever is in the slot of the control.
Place the other washer with the large I.D. from the parts bag next to lever, then the bushing. The smaller side of the bushing goes towards the lever and fits inside of the lever and the washer.
Discard the wave washer. Install the lock nut.
Check the alignment of the lever, bushing and washers to ensure that everything is aligned properly and torque the lock nut to 20 in. lbs. (2 Nm).
The control lever should move freely.
This engine speed control is set up with the "stop in the control". If a remote stop is desired remove and discard the short green wire that runs from the speed control grounding terminal (to the remote grommet stop blade). Reinstall the blade and screw. It will now be necessary to run a grounding wire to a remote grounding switch in order to stop the engine.
A remote grounding switch can be added to the engine at this terminal as well, thus allowing the engine to be stopped at either the stop in the control or the remote grounding switch.
27
OVM, OVXL, OHV VERTICAL SPEED CONTROL
This remote speed control may have governed idle, a choke override, and the option of an ignition remote stop terminal block.
The speed control is adjusted to the equipment throttle control by aligning the slot in the speed control lever with the alignment hole on the mounting bracket. Place a pin through the two holes, place the equipment throttle control to the wide open position, hook the bowden cable end in the control as shown, and tighten the cable housing clamp. In this position, the gap of
.040"
The idle speed is adjusted by turning the idle speed screw clockwise to increase engine R.P.M. and counterclockwise to decrease R.P.M. Use tool part # 670326 to adjust the high speed engine R.P.M. Place the slotted end of the tool onto the adjustment tab and bend the tab to the left (away from the control) to increase engine R.P.M.
Throttle plate alignment on all models with speed controls mounted on intake manifold. This adjusts choke in control as well (diag. 12 on page 25).
OHV
This speed control is adjusted to the equipment throttle control by aligning the slot in the speed control lever with the alignment hole on the mounting bracket. Place a pin through the two holes, place the equipment throttle control to the wide open position, hook the bowden cable end in the control as shown, and tighten the cable housing clamp. In this position, the gap of
.040"
NOTE: Assure that the throttle cable has full travel from wide open throttle to full choke. Hard starting could result if the cable is not properly adjusted to allow for full choke.
The idle speed is adjusted by turning the idle speed screw clockwise to increase engine R.P.M. and counterclockwise to decrease R.P.M. Use tool part
#670326 to adjust the high speed engine R.P.M. Place the slotted end of the tool onto the adjustment tab and bend the tab to the left (toward the spark plug end) to increase engine R.P.M.
OHV 11
DECREASE |
INCREASE |
|
|
Þ |
Þ |
|
|
HIGH SPEED |
.040 |
|
|
ADJUSTING LEVER |
(1.02 - 1.778 mm) |
||
BEND |
GAP LOCATION |
||
TO |
|
|
|
ADJUST |
CHOKE |
|
|
HIGH |
ADJUSTING |
|
|
SPEED |
TAB |
|
|
|
|
CONTROL LEVER |
|
|
|
HIGH SPEED |
|
|
|
PIN POSITION |
|
IDLE ADJUSTING |
|
|
|
SCREW |
|
|
|
|
OHV VERTICAL CONTROL |
25 |
|
|
|
|
|
CHOKE
HOOKUP
HIGH SPEED |
|
IDLE SPEED |
|
SCREW |
|
ADJUSTMENT |
|
|
|
|
|
TAB |
|
|
THROTTLE |
|
|
LINK HOOKUP |
|
|
ALIGNMENT |
|
|
HOLE |
|
|
|
|
CHOKE LEVER |
|
|
AIR GAP |
|
(.040 |
|
|
|
(1.02 - 1.778 mm) |
|
|
BEND TAB TO |
TOOL #670326 |
|
ADJUST |
|
|
|
OHV 11 - 17 HORIZONTAL CONTROL 26
LINKAGE BUSHING |
27 |
28
CHAPTER 5 RECOIL STARTERS
GENERAL INFORMATION
Recoil starters used on vertical shaft Tecumseh engines are top mount horizontal pull style. Horizontal shaft engines use recoil starters which can be mounted to pull either vertically or horizontally. All recoil starters turn the engine over by engaging a dog(s) into the starter cup attached to the engine flywheel. All starters are spring loaded to retract the dog(s) when the engine speed exceeds the turning speed of the starter.
OPERATION
As the starter rope is pulled, the starter pulley rotates on the center pin. The starter dog(s) is pinned or pocketed in the pulley hub and extend outward when the pulley rotation forces the starter dog(s) to contact the ears on the retainer. The retainer ears act as a ramp to fully extend the starter dog(s). The fully extended starter dog(s) locks in contact with notches in the starter cup. When the engine fires and the rotational speed of the starter cup exceeds the starter pulley, the starter dog(s) disengages from the starter cup. The starter dog spring(s) returns the starter dog(s) to the disengaged position. When the starter handle is released, the recoil spring turns the starter pulley in the opposite direction to retract the starter rope.
COMPONENTS
|
ROPE |
|
HANDLE |
|
STARTER HOUSING |
|
|
|
|
|
|
PULLEY AND
REWIND SPRING
ASSY.
STARTER DOG
DOG SPRING
WASHER
RETAINER
BRAKE SPRING |
|
WASHER |
|
SPRING PIN |
1 |
HANDLE |
|
|
|
|
|
HOUSING |
|
|
|
|
|
|
|
SPRING & |
|
|
|
|
|
|
|
KEEPER |
|
DOG SPRING |
|
|
|
|
|
|
|
|
|
|
|
|
|
||
|
|
|
|
|
DOG |
|
|
|
|
|
|
|
|
||
RETAINER |
|
|
|
|
|
|
|
|
|
|
|
BRAKE WASHER |
|||
|
|
|
|
||||
BRAKE SPRING |
|
|
|
|
|||
|
|
|
|
|
CAM DOG |
|
|
|
|
|
|
|
|
||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
CENTER |
2 |
|
|
|
|
|
|
SCREW |
|
|
|
|
|
|
|
|
|
SERVICE
Starter related problems will require the starter to be removed from the engine to diagnose the cause. Visually inspect the starter dog(s), starter cup, retainer, springs, rope, washers, and the starter pulley for wear or breakage. Use one of the following procedures that apply to the application to disassemble, repair, and assemble the starter. Always consult the Tecumseh Master Parts Manual for the correct replacement parts.
ROPE SERVICE
Rope replacement should be done using the correct part number replacement rope or braided rope of the correct diameter and length. Consult the Tecumseh Master Parts Manual to obtain the correct part number, length, and size required. Use the following rope chart to convert a numbered rope to a fractional diameter for bulk rope use. The rope ends should be cauterized by burning with a match and wiping the rope end with a cloth while hot.
29
CAUTION: HANDLE MATCHES SAFELY TO AVOID BURNS, AND EXTINGUISH COMPLETELY BEFORE DISCARDING.
#4 1/2 rope = 9/64" diameter (3.572 mm)
#5 rope = 5/32" diameter (3.969 mm)
#6 rope = 3/16" diameter (4.762mm)
ROPE RETAINER REPLACEMENT
1.Remove the starter handle if the retainer is a complete circle design. Remove the staple and old retainer.
2.Slide the rope retainer into the proper position and insert the staple using a pliers.
3.Install the starter handle and tie a left hand knot to secure the handle.
STAPLE
ONE PIECE ROPE RETAINER |
3 |
|
STYLIZED REWIND STARTER (OHH, OVRM,
OHM, OHSK, OVM, OVXL, OHV), and
STAMPED STEEL STARTER
Disassembly Procedure
1.After removing the rewind assembly from the engine blower housing, release the tension on the rewind spring. Remove the starter handle and carefully allow the rope to unwind into the starter housing (diag. 4).
2.Remove the decal or plastic disc in the center of the rewind.
3.Place a 1" (25.4 mm) deep well socket under the retainer. Set the rewind on a bench, supported on the socket.
4.Use a 5/16" (7.937 mm) or a [1/4" (6.35 mm) punch for stamped steel] roll pin punch to drive out the center pin. The stamped steel center pin is driven out from the outside, the punch tip must be angled inside the center hole. Move the punch around while driving the pin to help keep the pin straight.
CAUTION: THIS REWIND SPRING IS NOT SECURED IN A CANISTER. PULLEY BOSSES HOLD THE REWIND SPRING AND COVER, AND CAN BE EASILY DISLODGED DURING HANDLING.
5.Remove the brake spring, retainer, washers, and pulley assembly (diag. 4).
Note: The starter dogs face out on the stamped steel starter and the dogs face in on the stylized rewind starter.
6.All components in need of service should be replaced.
|
ROPE |
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HANDLE |
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STARTER HOUSING |
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PULLEY AND
REWIND SPRING
ASSY.
STARTER DOG
DOG SPRING
WASHER
RETAINER
KNOT
WASHER
SPRING PIN
4
5
30
Assembly Procedure
1. Reverse the disassembly procedure. The |
starter dogs with the dog springs must snap |
back to the center of the pulley (disengaged |
position). When the rope is pulled, the tabs |
on the retainer must be positioned so that they |
will force the starter dogs to engage the starter |
cup. (diag. 6 & 7) |
2. Install a new recoil spring if necessary by |
pushing the new spring out of the holder into |
the pulley cavity while aligning the outside |
STARTER HOUSING
HANDLE
HANDLE
INSERT
ROPE
PULLEY AND REWIND
SPRING ASSY.DOG SPRING
spring hook into the deep notch in the pulley. |
STARTER DOG
WASHER
Push the spring cover in until seated. |
3. Always replace the center spring pin with a |
new one upon reassembly. Place the two new |
plastic washers between the center leg of the |
starter and the retainer. New plastic washers |
are provided with a new center spring pin. |
Discard the old plastic washer. |
4. Place the rewind on a flat surface and drive |
the new center pin in until it is within 1/8" |
(3.175 mm) of the top of the starter. |
NOTE: DO NOT DRIVE THE CENTER PIN |
IN TOO FAR. |
RETAINER
BRAKE SPRING
WASHER
SPRING PIN
6
STARTER
HOUSING
HANDLE
ROPE
The retainer will bend and the starter dogs |
will not engage the starter cup. On the |
stamped steel starter the center pin should |
be driven in until it contacts the shoulder in |
the starter housing. |
5. Replacing rope wind the starter pulley |
counterclockwise four or five turns to |
PULLEY AND REWIND SPRING ASSY.
STARTER DOG
KNOT
DOG SPRING
WASHER |
RETAINER
BRAKE SPRING
the recoil spring and thread the rope through |
the starter housing eyelet. Pull enough rope |
through to tie a temporary knot in the rope. |
Reattach the starter handle to the rope using |
a |
allow the rope to recoil. |
STYLIZED REWIND STARTER WITH PLASTIC RETAINER
Disassembly Procedure
1.After removing the rewind assembly from the engine blower housing, remove the starter handle by first pulling a length of rope out using the handle, tying a temporary knot in the exposed rope, and either untying the knot in handle or prying out the staple.
2.Untie the temporary knot and slowly allow the rope to fully retract into the starter housing and the recoil spring to fully unwind.
3.Remove the decal from the center of the starter housing.
WASHER |
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SPRING PIN |
7 |
RETAINER WEDGE |
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STARTER |
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HOUSING |
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STARTER PULLEY |
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SPRING & COVER |
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DOG SPRING |
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STARTER DOG |
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DOG RETAINER |
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8 |
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31 |
4.Use a small Phillips screwdriver or similar tool to pry the retainer legs apart and lift out the retaining wedge.
5.Pinch the legs of the retainer together and pull on the head of the retainer to remove it from the housing.
6.Remove the pulley assembly from the recoil housing.
7.Repair or replace as necessary.
Assembly
1.If replacing the starter rope, see Step 8.
2.Install a new recoil spring if necessary by pushing the new spring out of the holder into the pulley cavity while aligning the outside spring hook into the deep notch in the pulley. Push the spring cover in until seated.
3.Apply a small amount of lithium grease to the inner bore of the center shaft.
4.Replace or check that both starter dogs are in the pulley pockets and that the dog springs are hooked on the outer surface of the dog.
5.Pinch the two legs of the plastic retainer together and start into the center shaft hole.
6.Rotate the retainer so the two tabs on the bottom of the part fit between the dog and pulley hub (left side of the dog). Push the retainer in until the leg prongs pop out of the center shaft.
7.Turn the starter over and snap the locking tab between the retainer legs, replace the top decal.
NOTE: Refer to Service Bulletin 122 for metal locking tab.
8.Wind the starter pulley counterclockwise four or five turns to
KEEPER SPRING STYLE STARTERS Disassembly Procedure
1.Untie the knot in the rope and slowly release the spring tension.
2.Remove the center screw, retainer (cam dog on snow proof type), starter dog(s) and dog spring(s), and brake spring (diag. 10).
3.Turn the spring and keeper assembly to remove the pulley. Lift the pulley out of the starter housing. Replace all worn or damaged parts.
RETAINING WEDGE |
(STEEL CLIP - NEW STYLE) |
STARTER |
HOUSING |
STARTER PULLEY |
SPRING & COVER |
DOG SPRING |
STARTER DOG |
DOG RETAINER |
9 |
STARTER HOUSING
REWIND
HANDLESPRING AND KEEPER ASSY.
HANDLE ROPE
INSERT
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PULLEY |
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DOG SPRING |
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STARTER DOG |
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DOG RETAINER |
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RETAINER SCREW |
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KNOT |
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CAM DOG |
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BRAKE SPRING |
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WASHER |
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SPRING PIN |
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"STAMPED STEEL WITH ROLL PIN" |
10 |
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32
Assembly Procedure
NOTE: This procedure covers three starters. Follow illustration of your starter type as shown.
1.Place the rewind spring and keeper assembly into the pulley. Turn the pulley to lock into position. A light coating of grease should be on the spring.
2.Place the pulley assembly into the starter housing.
3.Install the brake spring, starter dog(s), and starter dog return spring(s). The starter dog spring(s) must hold the dog(s) in against the pulley.
4.Replace the retainer cup (cam dog on snow proof starter) and retainer screw. Tighten to 65 - 75 in. lbs.
5.Tension the recoil spring by winding the pulley counterclockwise until it becomes tight, then allow the pulley to unwind until the hole in the pulley lines up with the rope eyelet in the starter housing. Install a knotted rope through the pulley and the eyelet and install the handle. A
HANDLE |
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HOUSING |
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SPRING & |
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KEEPER ASSY. |
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BRAKE SPRING |
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PULLEY |
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DOG SPRNG |
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RETAINER |
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RETAINER SCREW |
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"STAMPED STEEL" |
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CENTER PIN |
11 |
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STARTER HOUSING
REWIND
HANDLESPRING AND KEEPER ASSY.
HANDLE ROPE
INSERT
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PULLEY |
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DOG SPRING |
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STARTER DOG |
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DOG RETAINER |
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RETAINER SCREW |
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KNOT |
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CAM DOG |
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BRAKE SPRING |
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WASHER |
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SPRING PIN |
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"STAMPED STEEL WITH ROLL PIN" |
12 |
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HANDLE |
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HOUSING |
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SPRING & |
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KEEPER |
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DOG SPRING |
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PULLEY |
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DOG |
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RETAINER |
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BRAKE WASHER |
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BRAKE SPRING |
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CAM DOG |
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"ALUMINUM HOUSING" |
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CENTER SCREW |
13 |
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33
Stylized Starter (OHV 13.5
1.Remove the starter handle by first pulling a length of rope out using the handle, tying a temporary knot in the exposed rope, and untying the knot in the handle.
2.Untie the temporary knot and slowly allow the rope to fully retract into the starter housing and the recoil spring to fully unwind.
3.Remove the nut (using a 10 mm socket) and washers from the center leg of the recoil housing. Slowly unwind the dog spring by allowing the starter dog retainer to rotate.
4.Remove the starter dog retainer, starter dog spring, brake spring, and starter dogs.
5.Remove the starter pulley.
CAUTION: THE REWIND SPRING IS NOT SECURED IN PLACE. HOUSING BOSSES HOLD THE REWIND SPRING, AND THE SPRING CAN BE EASILY DISLODGED DURING HANDLING.
6.Remove the starter rope from the pulley if necessary.
Assembly
1.Replace the starter rope if removed by inserting one end through the hole in the side of the pulley and tying a left hand knot near the rope end. Pull the knot into the squared area and wind the rope counterclockwise (viewed from the pulley bottom) on the starter pulley.
2.Place the pulley on the housing center leg, align the end of recoil spring and the notch in the pulley and push down until seated.
3.Insert the starter dogs on the pulley pegs with the flat side away from the pulley, place the brake spring and starter dog spring on the pulley. The starter dogs must be free to retract into the pulley pocket.
4.Place the starter dog retainer on the center leg, hook the end of the dog spring into the hole in the retainer, press down and turn 1/2 a turn clockwise to line up the notches to the starter dogs, add the nylon washer, metal washer, lock washer, and hex nut. Tighten the hex nut to 40 inch pounds (4.5 Nm) torque.
NOTE: Type II - Apply blue Loctite to the center screw and torque to 70 in pounds (8 Nm).
5.Wind the pulley counterclockwise
6.Slide the starter handle on the end of the rope and secure using a left hand knot. Remove the temporary knot and allow the rope to retract.
STARTER HOUSING
REWIND SPRING
PULLEY
BRAKE SPRING
STARTER DOGS
STARTER DOG SPRING
KNOTSTARTER DOG RETAINER WASHER
LOCKWASHER 6mm METRIC NUT
TYPE I |
14 |
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STARTER HOUSING |
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SPRING AND |
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KEEPER |
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PULLEY |
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STARTER DOG |
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RETAINER SPRING |
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WASHER |
STARTER DOG |
STARTER DOG |
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BRAKE SPRING |
RETAINER |
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CENTER SCREW |
LOCKWASHER |
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TYPE II |
15 |
34
CHAPTER 6 ELECTRICAL SYSTEMS
GENERAL INFORMATION
The electrical system consists of three main elements: a battery, a starting circuit, and a charging circuit. The battery is part of both the starting and charging circuit. The battery should be checked before going into any extensive starter or charging system checks. If a battery has a shorted cell, overcharging can result, and the regulator or rectifier may appear to be at fault. If a cell has an open or high resistance connection, the electric starter operation will be affected.
The power source used to provide the energy to turn an electric starter motor on Tecumseh engines is either 120 volt A.C. current or 12 volt D.C. A 120 volt A.C. starter circuit utilizes a 120 volt power source instead of a battery. The 12 volt battery models require a charging system to maintain proper battery charge.
The starting circuit includes the battery, battery cables, starter or ignition switch, safety switches, starter solenoid, and an electric starter motor.
The charging system consists of alternator charge coils, rectifiers or diodes, regulator, ignition switch, flywheel magnets, and a battery. All engines that have a charging system will use a combination of some or all of these features.
OPERATION
STARTING CIRCUIT AND ELECTRIC STARTERS
After all of the safety interlock switches have been activated, the starter switch closes the starting circuit. A strong magnetic force is produced by the electrical current running through the armature windings. The armature magnetism repels the magnetism produced by the permanent field magnets of the electric starter. The repelling magnetic forces cause the armature to rotate, moving the drive pinion laterally on the splined armature shaft, meshing the starter pinion gear with the flywheel ring gear. When the drive pinion contacts the stop at the end of the armature shaft, the pinion rotates along with the armature shaft to crank the engine. The armature and pinion remain positively engaged until the engine fires and the flywheel rotates faster than the armature. The greater momentum of the flywheel throws the starter pinion gear out of mesh and forces the starter pinion back to the disengaged position. After the switch is released, the starting circuit is opened and the armature coasts to a stop.
Asmall
|
LOCK NUT |
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BOLT |
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BRUSHES |
END CAP |
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BRUSH SPRINGS |
WASHER |
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NUTS |
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BRUSH CARD |
||
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HOUSING
|
ARMATURE |
SPRING |
THRUST |
RETAINER |
WASHER |
RETAINER |
END CAP |
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SPRING GEAR |
ENGAGING NUT |
1 |
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DUST COVER |
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CHARGING CIRCUIT
The charging system works independently of any manual controls. The engine needs to be running to produce an electric current flow. When a conductor (alternating coils) cuts the magnetic field generated by the magnets in the flywheel, a current is induced in the alternator coil. The permanent magnets in the flywheel have a magnetic field in which the lines of magnetic force run from the North Pole to the South Pole. As the flywheel rotates and the position of the magnets change, the direction of the magnetic field changes or alternates. The alternating coils are wound in different directions to allow current to flow as an A.C. waveform (diag. 2).
ROTATION OF FLYWHEEL
2
35
CONVERTING ALTERNATING CURRENT TO DIRECT CURRENT
In order to charge a battery, it is necessary to convert alternating current (A.C.) to direct current (D.C.). This is accomplished by using a diode or rectifier (diag. 3). A single diode makes use of only one half of the A.C. signal and is known as HALF WAVE RECTIFICATION (diag. 4). This is acceptable in certain applications. In certain situations it is necessary to make use of the entire A.C. signal. To accomplish this, multiple diodes in a bridge configuration are used to produce FULL WAVE RECTIFICATION (diag. 5).
ANODECATHODE
BAND OR OTHER
MARKING INDICATES
CATHODE END
3
Current flows through a diode when the anode is more positive than the cathode. The cathode end of the diode should point toward the battery when diode is used between a charging system and a battery.
Half Wave Rectifier Single Diode
The single diode allows only the positive half of the A.C. signal through. It does not allow the negative portion through.
+ VOLTAGE |
HALF WAVE RECTIFIER |
|
(SINGLE DIODE) + VOLTAGE |
||
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A.C. INPUT |
|
D.C. OUTPUT |
4 |
- VOLTAGE |
- VOLTAGE |
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Full Wave Rectifier Bridge Rectifier |
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FULL WAVE RECTIFIER |
|
The full wave rectifier makes use of the entire A.C. |
|
(BRIDGE RECTIFIER) |
+ VOLTAGE |
|
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signal, converting it to D.C. |
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COMPONENTS |
- VOLTAGE |
A.C. INPUT |
BATTERY |
|
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The batteries used in conjunction with Tecumseh |
A.C. INPUT |
+ VOLTAGE (D.C.) |
|
||
engines are 12 volt lead acid or “maintenance free” |
|
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style. The chemical energy produced by the dissimilar |
+ VOLTAGE |
|
metals of the battery plates provides a electrical |
|
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potential that is used to power the electric starter or |
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unit accessories. Consult the original equipment |
|
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manufacturer’s service manual for battery size, |
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D.C. OUTPUT |
capacities, and testing procedure. |
- VOLTAGE |
5 |
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WIRING
The wires used in Tecumseh electrical systems are copper stranded with an insulated coating around the copper strands.
CONDITION: All wiring must be fully insulated between connection points, securely fastened and free of foreign material (such as rust and corrosion) at the connection points. This is especially important in the use of batteries where much of the potential may be lost due to loose connections or corrosion. Remember to check the insulation on the wire. All it takes is a pin hole for leakage to "ground out" on the engine or frame. This is of special concern when moisture or water is present.
36
WIRE GAUGE: The proper thickness of wire is |
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THE LARGER THE NUMBER THE SMALLER THE WIRE |
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necessary in all electrical circuits. Wire diameter is |
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measured in increments of gauge numbers. As the |
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gauge number of the wire increases, the wire diameter |
# 18 |
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decreases in size (diag. 6). |
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1.The starter circuit wiring must be rated at #6 or lower gauge number.
2. |
The charging circuit wiring must be rated at #16 |
# 6 |
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6 |
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or lower gauge number (20 amp system requires |
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#14 or lower gauge number). |
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3. |
The magneto circuit wiring (ground circuit) must |
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be rated at #18 or lower gauge number. |
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Tecumseh Products Company's standard wiring color codes effective August, 1992 are as follows:
Code |
|
Product |
Yellow |
- |
Alternator A.C. Leads |
Red |
- |
Alternator D.C. + Leads |
Brown |
- |
Alternator D.C. - Leads |
Black |
- |
Alternator Ground Leads, Battery Ground Leads |
Orange |
- |
12 Volt Starter B + Leads |
Dark Green |
- |
Ignition |
NOTE: PRIOR TO AUGUST 1992, WIRE CODES CHANGED ACCORDING TO MODEL AND SPECIFICATION NUMBERS.
ELECTRICAL TERMS
ALTERNATOR - An alternator consists of coils of wire wound around a metal lamination stack. When a magnet is moved past the coils, a current is induced in the coils. In general, the greater the number of coils, the greater the output of the alternator.
RECTIFIERS and DIODES - Charging a battery requires that the alternating current produced by the alternator be changed to direct current. This is accomplished by using a diode or rectifier.
REGULATOR/RECTIFIERS - This combines a regulator with a rectifier. The regulator prevents overcharging of the battery and the rectifier changes the alternating current to direct current.
CONDUCTORS - A conductor is a material that allows an electric current to pass through it. All metals are conductors of electricity, but some are better conductors than others. Silver, copper and gold are some of the better known conductors.
INSULATORS - An insulator is a material that will not allow an electric current to pass through it. Some of the more common materials that are insulators are glass, plastic, rubber, ceramics and porcelain.
BASIC CHECKS
Before going into extensive checks, be sure to perform the more basic checks first, such as:
1.Battery defective or not charged.
2.Corroded or loose terminals or connections, or wrong connections.
3.Cracked insulation or broken wires.
4.A wire "grounding out" in the system.
5.Defective switch.
6.Operator presence system functioning properly.*
*NOTE: ALL LAWN AND GARDEN TRACTORS BUILT AFTER JULY OF 1987 ARE REQUIRED TO HAVE AN OPERATOR PRESENCE SYSTEM AND MANY CAME EQUIPPED WITH SUCH A SYSTEM PRIOR TO THIS DATE. IF THE TRACTOR IS "CUTTING OUT" OR WILL NOT START, THIS IS AN AREA THAT SHOULD BE CHECKED OUT.
37
TROUBLESHOOTING ELECTRICAL STARTER CIRCUIT FLOW CHART
Starter will not
turn
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NO |
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YES |
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Is there power |
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at the power |
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source? |
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Intermittent
starter operation
Starter turns at
low rpms or
stalls under load
Repair or |
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NO |
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replace power |
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source |
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Check wiring, connections, safety switches, starter switch
Is power supplied to the
starter terminal?
YES
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Isolate engine |
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NO |
from the |
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equipment, |
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does engine |
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turn over? |
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YES
Check starter
for binding
brushes, worn
brushes, dirty or oily commutator
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Repair or replace |
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Remove spark |
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NO |
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equipment |
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plug, does engine |
YES |
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causing |
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turn over freely? |
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excessive |
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loading |
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Internal engine
failure or flywheel
interference
|
Reinstall spark |
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NO |
plug, does |
YES |
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engine bind on |
|||
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compression |
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stroke? |
|
Repair or replace
electric starter
NO
Internal engine failure repair or replace engine
Check valve lash.
Adjust if
necessary. Does the engine turn over without binding now ?
Internal engine failure repair or replace engine
38
TROUBLESHOOTING ELECTRICAL CHARGING CIRCUIT FLOW CHART
NO
Identify the charging system used by model and specification number or visually checking the electrical plug
Consult the Mechanic's Handbook or Electrical Troubleshooting booklet for test procedure for the charging system used
Test for either AC or DC voltage as directed at the proper engine
RPM
Is the voltage greater than or equal to the minimum value?
YES
NO |
Is AC voltage before diode or |
YES |
||
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rectifier greater than the |
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minimum value? |
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Check wiring, switches, or ammeter for breaks, shorts
Alternator coil failure, replace coil assy.
Check diodes,
replace if no
continuity exists or if
continuity exists
reversing test leads
Check fuses, replace
as necessary
Check switches,
wiring, or lights for
shorts
39
TESTING PROCEDURE
STARTING CIRCUIT
1.Check the power source using an electrical tester and following the tester's recommended procedure. Make sure the battery meets the minimum battery voltage requirements found in the original equipment manufacturer's service manual.
2.Check the electric starter terminal for the required voltage (12v D.C. or 120v A.C.) using a voltmeter.
CAUTION: FOLLOW ALL SAFETY PRECAUTIONS WHEN TESTING FOR A.C. VOLTAGE, ELECTRIC SHOCK CAN KILL.
3.Check wiring, connections, fuses, ignition or starter switch, safety switches, or solenoid for continuity using a ohmmeter or a continuity light. Repair or replace as necessary.
4.Remove all equipment loads from the engine. Take off all drive belts, chains, and couplers to isolate the engine from the equipment it is powering.
5.Try to turn the engine over using the recoil assembly if equipped. If the engine doesn’t turn over, a mechanical binding may be the cause. Check for proper lubrication (oil level and viscosity) and check for electric starter gear and flywheel ring gear interference. If no problem is discovered, the problem is an internal failure.
6.If the engine binds only on the compression stroke, check the engine valve clearance per the specification table in Chapter 10. If the valve clearance is within the specifications, the camshaft (compression release failure) may require replacement. Valve clearance not within the listed specifications will require resetting the rocker arms to obtain the proper clearance.
7.If the engine turns over freely, the electric starter should be replaced or disassembled and checked. See "Service" in this chapter. 120 volt starters labeled UL Listed/CSA Approved can be serviced; however, starters labeled CSA must only be replaced. If the preceding steps fail to correct the problem, the engine will require to be disassembled to find the mechanical failure. See Chapter 9 under "Disassembly Procedure".
CHARGING CIRCUIT
The following pages will show wiring diagrams of several Tecumseh charging systems. The charging system used on the engine is best identified by obtaining the engine model number and the specification number on the engine. Consult a Tecumseh dealer or a parts manual to identify the charging system. To make many of the tests it is necessary to run the engine and measure alternator output with a voltmeter. When making voltage tests with the engine running, it is not necessary to take readings at all the listed R.P.M.s. Checking at one of the speeds is sufficient.
In some cases an open circuit D.C. check cannot be made. A SCR (Silicon Controlled Rectifier) is located in the circuit which requires a minimum “turn on” voltage to allow it to conduct. Without the battery in the circuit this “turn on” voltage is not present. The SCR “senses” this and there will be no D.C. output from the regulator / rectifier.
Each charging system has its own testing procedure. Test the charging system using the applicable procedure found on the following pages.
350 Milliamp Charging System
CHECKING THE SYSTEM: The battery must be in the circuit to perform the test properly. Set the voltmeter to the 0 - 20 D.C. volt scale. Connect a voltmeter across the battery. The voltmeter should read the battery voltage. Start the engine. With the engine running, there should be an increase in the voltage reading. If there is no change in the voltage reading, the alternator is defective and should be replaced. See Chapter 9 for "Disassembly Procedure" (diag. 7).
(+) POSITIVE LEAD
MAGNETO GROUND |
D.C. OUTPUT |
(GR) |
LEAD (RED) |
BATTERY GROUND (BL) |
ELECTRIC STARTER |
LEAD (ORG) |
BLACKRED
7
40
18 Watt A.C. Lighting Alternator
CHECKING THE SYSTEM: To check the system, disconnect the plug from the rest of the lighting system. Connect a wire lead from the single pin connector coming out of the engine to one terminal of a No. 4414, 18 watt bulb. Connect another wire lead to the other terminal of the bulb and run to a good ground on the engine. Start the engine and test the circuit using the A.C. voltmeter as shown (diag. 8).
With the engine running, minimum A.C. voltage across the bulb should be:
2000 R.P.M. - 6.0 Volts A.C.
3000 R.P.M. - 8.5 Volts A.C.
3600 R.P.M. - 10.0 Volts A.C.
If minimum values are noted, the alternator is okay. If less than the minimum values, the alternator is defective. See Chapter 9 for "Disassembly Procedure".
3 AMP
Before making any exterior tests, check for inoperative switch, shorted wires and burned out headlight and/ or stop tail light. To check out the alternator, check the A.C. lead to ground at each yellow wire (diag. 9).
With engine running, minimum values should read: 2500 R.P.M. - 8.0 Volts A.C.
3000 R.P.M. - 9.5 Volts A.C.
3300 R.P.M. - 10.5 Volts A.C.
3600 R.P.M. - 11.5 Volts A.C.
It the above minimum readings are noted, the alternator is okay. Check for defective lights, wiring or switches, if less than the above readings, the alternator is defective. See Chapter 9 for "Disassembly Procedure".
NOTE: ON OLDER POINT IGNITION SYSTEMS, THE A.C. OUTPUT LEADS ARE BLACK AND RED.
2.5 Amp D.C., 35 Watt Lighting
To check this system follow the meter hook ups at the right, checking the D.C. neg and D.C. positive first. If output is below standard listed pull back protective coating in front of the diode and check A.C. output. If A.C. is good check each diode it services as requested see parts list.
D.C. valve (+) or
R.P.M. D.C. Volts |
R.P.M. |
Volts A.C. |
||||
2500 - 8.0 |
Volts D.C. |
2500 |
- |
18 Volts A.C. |
||
3000 |
- 9.5 |
Volts D.C. |
3000 |
- |
22 Volts A.C. |
|
3300 |
- |
10.5 Volts D.C. |
3600 |
- |
26 Volts A.C. |
|
3600 |
- |
11.5 Volts D.C. |
|
|
|
|
NOTE: These minimum numbers should be obtained by your meter and will often be higher.
ENGINE
YELLOW
#4414 BULB |
8 |
|
YELLOW
YELLOW
A.C.GREEN IGNITION STOP
YELLOW 9
TWO DIODES |
D.C. |
RED
D.C. NEGATIVE OUTPUT LEAD (BROWN D.C.)
D.C. POSITIVE OUTPUT LEAD (RED D.C.)
D.C.
A.C.
10
41
3 AMP DC ALTERNATOR SYSTEM - DIODE IN HARNESS SLEEVE
This system has a diode included in the red wire which converts the alternating current (A.C.) to direct current. The direct current (D.C.) is used to provide a trickle charge for the battery. The leads from the alternator and the type of connector may vary, but the output readings will be the same.
CHECKING THE SYSTEM: Remove the fuse from fuse holder and check the fuse to make certain it is good. If faulty, replace with a six (6) AMP fuse.
To check D.C. output, separate the connectors at the engine. Place the probe (+) in the red wire lead connector. Ground the other probe to the engine (diag. 11).
With the engine running minimum values should read: 2500 R.P.M. - 8.0 Volts D.C.
3000 R.P.M. - 9.5 Volts D.C.
3300 R.P.M.
3600 R.P.M.
If one of these minimum readings are noted, the system is okay. Check for bad battery, ammeter, wiring, etc.
If no reading or less than the above reading, proceed to make an A.C. output check by pulling back the protective coating from the wire on the alternator side of the diode. Test the A.C. voltage before the diode using an A.C. voltmeter.
With the engine running minimum values should read: 2500 R.P.M. - 18.0 Volts A.C.
3000 R.P.M. - 22.0 Volts A.C.
3300 R.P.M. - 24.0 Volts A.C.
3600 R.P.M. - 26.0 Volts A.C.
If low or no voltage is experienced, replace the alternator. If the alternator puts out the minimum A.C. voltage, replace the diode.
To replace the diode, disconnect at plug (spade terminal) and cut the wire on the opposite end of the diode at the solderless (crimped) connector. Remove 1/4" (6.35 mm) of insulation from the cut end of the wire and twist the strands together. Place the solderless connector from the new diode onto the exposed 1/4" (6.35 mm) wire and crimp the connector with a standard electricians pliers. Reconnect plug end (or spade connector (diag. 12).
NOTE: DO NOT USE ACID CORE SOLDER. BE CAREFUL NOT TO APPLY HEAT DIRECTLY TO THE DIODE - USE A HEAT SINK.
New heat shrink tubing can be installed by slipping over the wires and heating with a hot air gun. If this is not available, tape the diode and connections with electrical tape.
RED
DIODE
GREEN
D.C.
11
SPADE |
SOLDERLESS |
|
CONNECTOR |
||
CONNECTOR |
||
|
||
Þ |
|
|
FUSE HOLDER |
|
|
|
12 |
IF BULB DOES NOT LIGHT OR LIGHTS WHEN
POLARITY REVERSED, DISCARD DIODE.
13
42
5 AMP D.C. ALTERNATOR SYSTEM
CHECKING THE SYSTEM: An open circuit D.C. voltage check cannot be made with this system. If a known good battery fails to maintain a charge, proceed to make an A.C. voltage test.
To do this, the blower housing must be removed, and the
CAUTION: AT NO TIME SHOULD THE ENGINE BE STARTED WITH THE BLOWER HOUSING REMOVED.
With the engine running, the minimum values should read:
2500 R.P.M. - 19.0 Volts A.C.
3000 R.P.M. - 23.0 Volts A.C.
3300 R.P.M. - 26.0 Volts A.C.
3600 R.P.M. - 28.0 Volts A.C.
If the minimum values are noted, the alternator is ok and the
INSERT PROBES INTO CONNECTOR SLOTS. DO NOT REMOVE CONNECTOR WIRES.
YELLOW
RED
NOTE: D.C. OUTPUT MUST BE DISCONNECTED TO PERFORM A.C. OUTPUT TEST.
A.C. VOLTMETER
CAUTION: BLOWER HOUSING MUST BE |
14 |
INSTALLED WHEN RUNNING ENGINE |
3 Amp D.C. 5 Amp A.C. Alternator
This unit combines a 3 Amp D.C. system used to charge a battery with a 5 Amp A.C. system used for lighting. Located in the red wire of the harness is a diode which converts the alternating current to direct current for charging the battery. The yellow wire provides the A.C. voltage for the lighting circuit.
A wire harness( part # 36588) may be added to the 3 Amp D.C. / 5 Amp A.C. charging system to power an electric clutch without the use of a battery. Test the charging system using the applicable " Checking the System " procedure listed in this section. Test the diode in the harness by using a continuity test (diag.
15)Continuity should exist in one direction only. Replace the diode if continuity exists after reversing tester leads or no continuity is found. Use the procedure for diode replacement found in the 3 AMP alternator test (diag. 12).
RED LEAD |
DIODE |
3 AMP D.C.
BLACK LEAD
5 AMP A.C.
15
43
CHECKING THE SYSTEM: To check the system, disconnect the plug and measure the D.C. voltage at the red wire terminal (diag. 16). Measure the A.C. voltage at the yellow wire terminal. With the engine running, the minimum values should be:
MODELS OVM/OVXL/OHV12.5
3 Amp D.C. (Red wire)
2500 R.P.M. - 8.0 Volts D.C.
3000 R.P.M. - 11.0 Volts D.C
3600 R.P.M. - 13.0 Volts D.C.
5 Amp A.C. (Yellow wire)
2500 R.P.M. - 8.5 Volts A.C.
3000 R.P.M. - 11.0 Volts A.C.
3600 R.P.M. - 13.0 Volts A.C.
MODELS OHV 13.5 - 17.0 (3/5 amp split)
3 Amp D. C. (Red wire)
2500 |
R.P.M. - |
6.5 Volts D. C. |
3000 |
R.P.M. - |
9.0 Volts D. C. |
3600 |
R. P.M. - 11.0 Volts D. C. |
|
5 Amp A.C. (Yellow wire)
2500 R.P.M. - 15.0 Volts A.C.
3000 R.P.M. - 18.0 Volts A.C.
3600 R.P.M. - 22.0 Volts A.C.
If the above minimum values are noted, the system is okay. Check for defective lights, wiring or switches. If less than above values are noted, pull back the protective shrink tubing from the diode. Using an A.C. voltmeter, check the voltage going into the diode from alternator, at the lead on the alternator side of the diode (diag.17). If low or no voltage is experienced, replace the alternator.
Models OVM/OVXL/OHV12.5 (Red between Engine and Diode)
With the engine running, the minimum values should read:
2500 R.P.M. - 20.0 Volts A.C.
3000 R.P.M. - 25.0 Volts A.C.
3300 R.P.M. - 26.5 Volts A.C.
3600 R.P.M. - 29.0 Volts A.C.
RED
DIODE
YELLOW
D.C.
16
DIODE
RED
YELLOW
A.C.
17
DIODE
A.C.
18
44
Models OHV 13.5 - 17
(Read between Engine and Diode)
2500 R.P.M. - 17.0 Volts A.C.
3000 R.P.M. - 21.0 Volts A.C.
3600 R.P.M. - 24.5 Volts A.C.
If low or no voltage is experienced, replace the alternator. If the alternator puts out the minimum A.C. voltage, replace the diode.
A.C.
RED
DIODE
YELLOW
19
7Amp D.C. Alternator System Regulator- Rectifier Under Engine Housing
In this system, the regulator and rectifier are combined in one solid state unit mounted under the blower housing of the engine.
Various types of
CHECKING THE SYSTEM: An open circuit D.C. voltage check cannot be made with this system. If a known good battery fails to maintain a charge, proceed to make an A.C. voltage test.
To do this, the blower housing must be removed, and the
Keep the A.C. leads attached to the
CAUTION: AT NO TIME SHOULD THE ENGINE BE STARTED WITH THE BLOWER HOUSING REMOVED.
With engine running, minimum A.C. voltage from lead to lead should be:
2500 R.P.M. - 16.0 Volts A.C.
3000 R.P.M. - 19.0 Volts A.C.
3300 R.P.M. - 21.0 Volts A.C.
3600 R.P.M. - 23.0 Volts A.C.
If the minimum readings are noted, the alternator is okay. If the system fails to charge a known good battery, the
MAGNETO GROUND - GREEN
D.C. OUTPUT |
20 |
|
INSERT PROBES INTO
CONNECTOR SLOTS DO
NOT REMOVE
CONNECTOR WIRES
CAUTION: BLOWER |
YELLOW |
HOUSING MUST BE |
|
INSTALLED WHEN |
|
RUNNING ENGINE |
RED |
|
|
|
A.C. VOLTMETER |
21
45
10 Amp A.C. Alternator
CHECKING THE SYSTEM: Unplug the connector at the wiring harness supplied by the OEM. Proceed to make an A.C. output check. Place one lead of the A.C. voltmeter on the center plug of the connector. Place the other lead to engine ground (diag. 22).
With the engine running, minimum values should read: 2500 R.P.M. - 16.0 Volts A.C.
3000 R.P.M. - 20.0 Volts A.C.
3300 R.P.M. - 22.0 Volts A.C.
If less than above output, the alternator assembly is defective. See Chapter 9 for "Disassembly Procedure".
A.C. OUTPUT
YELLOWA.C.
22
16 Amp Alternator System with External Regulator
CHECKING THE SYSTEM: An open circuit D.C. voltage check cannot be made with this system. If a known good battery fails to maintain a charge, proceed to make an A.C. voltage test.
Disconnect the red D.C. output connector at the wiring harness and connect the probes from an A.C. voltmeter to the wire terminals at the
With the engine running, minimum values should read:
2500 R.P.M. - 21 Volts A.C.
3000 R.P.M. - 26.5 Volts A.C.
3600 R.P.M. - 31.0 Volts A.C.
If the minimum values are noted, the alternator is operating properly. If less than the above values are noted, the alternator is defective.
VOLTAGE REGULATORS
If a known good or load tested battery fails to maintain a charge, the charging system and the regulator can be checked using a voltmeter. Set the voltmeter on the
FUEL
If the engine is running, the solenoid can be checked by removing the electrical
Test the solenoid off the carburetor by applying 12 volt D.C. from the battery positive terminal to the (or one) solenoid terminal. Connect a jumper wire from the metal housing (or other terminal) to a negative battery terminal. The plunger should retract the full travel distance. Disconnect the negative jumper lead and the plunger should return to the extended position. Replace if necessary (diag. 24).
D.C. OUTPUT - RED
SOLENOID LIGHT
GREENSWITCH
MAGNETO
GROUND
FUSE
BATTERY
AMMETER
REGULATED
D.C. OUTPUT
YELLOW
|
|
RED |
|
NOTE: D.C. OUTPUT MUST BE DISCONNECTED TO |
23 |
||
PERFORM A.C. OUTPUT TEST. |
|||
SINGLE |
DOUBLE |
24 |
|
46
LOW OIL SHUTDOWN SWITCHES
Check the LOS switch while it is in the engine. The engine must be level, and the oil level at the full mark. Place the speed control in the run position. Remove the spark plug wire from the spark plug. Install a gap type tester connected to the spark plug wire and a good engine ground. Spin the engine over using the electric or recoil starter. A bright blue spark should be seen at the tester. If not, remove the blower housing and disconnect the LOS lead from the ignition module. Reinstall the blower housing and spin the engine over. If spark occurs now, replace the LOS switch. If no spark is seen, replace the ignition module.
If equipped, the indicator light will flash if the oil level is at or below the add mark and the engine is turned over while attempting to start.Test by turning the engine over with the oil level below the add mark. If the indicator light does not flash, replace the indicator light.
INDICATOR LIGHT
26
FLOAT
SWITCH
25
LIGHTED ENGINE ON/OFF ROCKER SWITCH
W/LOW OIL SHUTDOWN
TERMINALS
(3)
27
ENGINE ON/OFF ROCKER SWITCH
TERMINALS
(2)
SPACER
28
47
LOW OIL PRESSURE SENSOR
Test the sensor on a running engine using an ohmmeter or continuity tester with one tester lead connected the sensor terminal (with lead wire removed) and the other to an engine ground. An open circuit should be found with the engine running and continuity should exist when the engine is shut off. If continuity is found or the tractor oil pressure indicator light is on or comes on at low engine RPM's, remove the sensor and check engine oil pressure with a master oil pressure gauge. The oil pressure of a running engine should be above 10 p.s.i. (.700 bar). If lower than 10 p.s.i. (.700 bar), an internal engine problem exists (diag. 29).
29
LOW OIL SENSOR
This sensor must use a # 194 bulb in series with the sensor for proper operation and to prevent sensor damage. Remove the sensor from the engine and attach the electrical plug. Attach a jumper lead from an engine ground to the threaded portion of the sensor. Place the keyswitch in the run position. The indicator light should come on with the tip of the sensor in air and go off when oil covers the sensor tip. The response time of the sensor is between 5 and 15 seconds with 13 volts D.C. at the battery. Lower battery voltage will result in a longer response time. Use
ELECTRIC STARTER SERVICE
30
This section covers the service procedures for the 12 and 120 volt electric starters. For diagnosis of the starting circuit see “Electrical Starter Troubleshooting” in this chapter. Illustrations may not be identical in configuration to the starter being serviced, but procedures and tests apply unless otherwise stated. Starters labeled UL listed/ CSA approved are serviceable. Starters labeled CSA cannot be serviced, only replaced. If a starter is serviced, the "O" rings on each end of the housing must be replaced.
12 VOLT or 120 VOLT ELECTRIC STARTERS
1.Remove the plastic dust cover on the bendix end (diag. 31).
2.Push down the spring retainer and remove the retainer ring.
3.Slide off the spring retainer,
4.If internal service is necessary
5.Remove the two or four retaining nuts from the through bolts holding the cap assembly.
6.Slide off the cap assembly. The terminal insulator slides out of the commutator cap (some models).
7.Remove the armature.
8.Inspect and replace as necessary, see the section "Inspection and Repair" later in this chapter. Use the reverse procedure for assembly. ( For ease of assembly, place the armature into the brush end of the frame first.)
BRUSHES
GASKET
ARMATURE
|
THRUST |
|
WASHER |
RETAINER & |
|
SPRING |
|
BENDIX ASSEMBLY |
|
RETAINING RING |
|
DUST COVER |
31 |
|
48
Inspection And Repair
1. The pinion gear parts should be checked for |
damage or wear. If the gear does not engage |
or slips, it should be washed in solvent (rubber |
parts cleaned in soap and water) to remove dirt |
and grease, and dried before reassembly. Also |
check the armature and drive nut splines for |
wear or damage. Replace parts as necessary. |
2. The brushes and brush card holder should be |
checked for wear. With the armature in place |
and the brushes engaging the commutator |
surface, check the brushes for wear. Brushes |
should be replaced if the brush wire approaches |
the bottom of the brush holder slot. Brush |
springs must exhibit enough strength to keep |
tension on the brushes and hold them on the |
commutator. |
3. The field windings can be checked using a |
continuity light or ohmmeter. Attach one lead |
to each field coil connection. Continuity should |
exist between each field coil connection, and |
no continuity should exist between the field coil |
connections and the starter housing (diag. 32 |
& 33). |
4. The armature should be checked for glazing or |
wear. If necessary the armature can be turned |
down in a lathe. While rotating, polish the |
commutator bars using a piece of 00 sandpaper |
(diag. 34). Light pressure and back and forth |
movement should be used. Recut the |
commutator bars to a depth equal to the width |
of the insulators between the bars. Check for |
FIELD COIL
CONNECTORS
BRUSH
SPRINGS
12 VOLT |
32 |
FIELD COIL
CONNECTORS
CONNECTION POINT OF POWER CORD LEADS
120 VOLT |
33 |
continuity between the copper commutator bars |
and the iron of the armature, none should exist |
(diag. 35). |
34 |
35 |
Brush Card Replacement
1.Loosen but do not remove the two nuts on the starter terminal post.
2.Remove the nuts holding the end cap in place. Remove the end cap and the thrust washer.
3.Grasp the thru bolts using a vise grip positioned as close to the flanged end as possible to prevent thread damage. Remove the two nuts holding the driving end cap in place. Remove the armature and driving cap assembly, followed by the two thru bolts. Notice the position of the brush ground eyelet under the thru bolt flange.
4.Note or mark the position of the connectors of the brush wires. Use a wire cutter to clip the solid field wires as close to the connectors as possible.
5.Note or mark the brush card in the starter housing, and remove the brush card assembly. Clean the accumulated dirt off all starter parts. Scrape the insulating varnish off the last 1/2" (12.7 mm) of the solid field wires.
6.Insert the new brush card into position while guiding the solid field wires through the proper slots in the brush card.
7.Crimp and solder the brush leads to the solid field wires. Use a needle nose pliers or vise grip to hold the woven brush lead close to the connector while soldering. This prevents solder and heat from flowing up the brush lead. Insulate the crimped connection nearest the starter terminal post using electrical tape or heat shrink tubing. Route the wires to prevent damage during assembly.
8.Install the armature into the housing while spreading the brushes. Install the thru bolts while checking to make sure the bolts go thru the ground brush eyelet terminals. Install and tighten the drive end thru bolt nuts, but do not overtighten.
9.Install the thrust washer on the end of the armature and the install the starter end cap. Secure the cap with the locking nuts and tighten the nut on the starter terminal post. Rotate the armature by hand to check for binding before installation on the engine.
49
CHAPTER 7 FLYWHEEL BRAKE SYSTEMS
GENERAL INFORMATION
Tecumseh’s brake systems are required to meet compliance standards which has become a federal law as of June 30, 1982. Listed below are two methods used by original equipment manufacturers to meet compliance standards.
1.Use of the blade brake clutch in conjunction with a top mounted recoil starter or 12 volt electric starter. The blade must stop within three seconds after the operator lets go of the blade control bail at the operator position and the engine continues to run. Starter rope handle is either on the engine or on the equipment handle.
2.Use of a recoil starter with the rope handle on the engine as opposed to within 24 inches (61 cm) of the operator position. This method is acceptable if the mower deck passes the 360 degree foot probe test. A specified foot probe must not contact the blade when applied completely around the entire blade housing. This alternative can be used with engine mounted brake systems and typical bail controls. The blade must stop within three seconds after the operator lets go of the engine/blade control bail at the operator position and the engine is stopped.
Tecumseh’s flywheel brake system provides consumer safety by killing the engine and stopping the lawnmower blade within three seconds after the operator releases the engine/blade control bail at the handle of the lawnmower. This system is available on recoil and electric start models. The engine stopping time is affected by the engine R.P.M. Consult microfiche card # 30, the Plus 1 or Parts Smart
OPERATION
In the stop position the brake pad is applied to the inside edge of the flywheel, at the same time the ignition system is grounded out (diag. 1).
In order to restart the engine, the engine/blade control bail must be applied. This action pulls the brake pad away from the inside edge of the flywheel and opens the circuit to the ignition ground out terminal. On electric start systems the starter is energized by an ignition/start switch or a two motion control. On nonelectric start systems, the recoil starter rope must be pulled to start the engine (diag. 2).
GROUND
CLIP
IGNITION
GROUND
WIRE
|
BRAKE |
|
PAD |
BRAKE "ON" |
1 |
GROUND
CLIP
IGNITION
GROUND
WIRE
BRAKE "OFF" |
2 |
50
COMPONENTS
The brake bracket assembly consists of a replaceable brake lever and pad, an ignition kill switch, and a tension spring (diag. 3). Late production brake brackets are serviced as a complete assembly.
The ignition ground terminal is a plastic block with a wire extending out of it. The wire is connected to the ignition ground out spade on the solid state module. The brake lever contacts the wire of the ignition ground terminal when the engine/blade control bail is released, and the ignition module is grounded. This stops the solid state module from firing the spark plug (diag. 3).
The interlock switch is a push button switch that is activated by the brake lever when the engine/blade control is actuated. If there is a electric starter switch used to start the engine, the interlock switch acts as a safety switch and will not allow the starter to crank unless the engine/blade control bail is depressed.
Where a two motion control is used the interlock switch is utilized as the starter switch.
The brake spring supplies the pressure to the brake lever and brake pad to stop the flywheel.
The control cable transfers the motion of the engine/ blade control bail to the brake system.
GROUNDING |
TOP VIEW |
LINKAGE |
CLIP POSITION |
|
|
|
|
BRAKE PAD |
3 |
Ô
MOUNTING HOLES |
Ô |
MECHANISM FULL DOWN |
|
BEFORE SCREWS TORQUED |
ELECTRIC START INTERLOCK SWITCH
4
SERVICE
Service on part or all of the flywheel brake assembly will require a partial disassembly of the engine to allow the flywheel and brake bracket to be removed.
Remove the necessary components using steps
51
BRAKE BRACKET ASSEMBLY
Late production brake brackets are serviceable only by installing a complete brake bracket assembly.
On serviceable brake brackets, continue by removing the alignment tool. Release the spring tension by unhooking the short end of the spring from bracket with a pliers. Remove the “E” clip from the brake pad shaft. Slide the pad lever from the shaft and unhook the link. Inspect the brake pad for dirt, oil or grease contamination. If the pad is contaminated, or if there is less than .060" (1.524 mm) thickness of brake pad material at the pad's thinnest point, replacement is necessary. The brake pad is bonded to the brake lever and must be replaced as an assembly. Rehook the link, install the brake lever and pad assembly, install the "E" clip, rehook the short end of the spring and continue to reassemble the brake system in the reverse order of disassembly.
IGNITION GROUNDOUT TERMINAL
Inspect the terminal grounding wire for proper alignment and contact with the brake arm. Insure that all electrical connections are clean and secure (diag. 5).
STARTER INTERLOCK SWITCH
The engine/blade control must close the interlock switch before the starter can be engaged. To check the interlock switch, use an ohmmeter or continuity light to perform a continuity check. Disconnect the wires off the switch before performing a continuity check. Continuity should exist between the two terminals when the interlock switch button is completely depressed. No continuity should exist when the button is released. If the switch fails replace the switch (diag. 6).
To replace the interlock switch, carefully grind the heads off of the rivets that fasten the interlock switch to the brake bracket. Remove the rivets from the back side of brake bracket. Use the
GROUNDING |
TOP VIEW |
LINKAGE |
CLIP POSITION |
|
|
|
|
BRAKE PAD |
5 |
Ô
MOUNTING HOLES
MECHANISM FULL DOWN Ô
BEFORE SCREWS TORQUED
ELECTRIC START INTERLOCK SWITCH |
6 |
|
CONTROL CABLE
If replacing the cable conduit screw with a screw other than a service part replacement, be certain that the screw length is not too long as to prevent free travel of the lever.
Make sure the button on the starter interlock switch is completely depressed when the control is fully applied. The cable must provide enough travel so the brake will contact the flywheel. Some slack should exist in the cable adjustment to compensate for brake pad wear (diag. 7).
SCREW END MUST
NOT BLOCK LEVER
ACTION
CABLE CLAMP
SCREW
7
BRAKE BRACKET REPLACEMENT
When installing a inside edge brake bracket assembly, be sure the slotted holes in the brake bracket are all the way down on the fasteners. This will properly align the brake bracket to the flywheel brake surface (diag. 8).
When completed, check for less than 3 second stop time.
MOUNTING HOLES
Ô
Ô
MECHANISM FULL DOWN
BEFORE SCREWS TORQUED
8
52
CHAPTER 8 IGNITION
GENERAL INFORMATION
Overhead valve four cycle Tecumseh engines use solid state capacitor discharge modules to provide high voltage to fire the spark plug. This is an all electronic ignition system with all the components located outside the flywheel. The modules look similar but are not interchangeable. If necessary, the correct replacement module should be found using the Master Technician's Parts Manual.
The solid state ignition system consists of flywheel magnets and a flywheel key, charge coil, capacitor, a silicon controlled rectifier, pulse transformer, trigger coil, high tension lead, and a spark plug. Everything except the flywheel magnets, key and the spark plug are located in a encapsulated ignition module. This solid state (CDI) module is protected by epoxy filler from exposure to dirt and moisture. This system requires no maintenance other than checks of the high tension lead and spark plug.
OPERATION
SOLID STATE IGNITION SYSTEM (CDI)
As the magnets in the flywheel rotate past the charge coil, electrical energy is produced in the module. The energy is stored in the capacitor ( approx. 200 volts) until it is released by an electrical switch (SCR). As the magnet continues to rotate, it passes past a trigger coil where a low voltage signal is produced. This low voltage signal closes the SCR switch, allowing the energy stored in the capacitor to flow to a transformer where the voltage is increased from 200 volts to 25,000 volts. This voltage follows along the high tension lead to the spark plug where it arcs across the electrodes and ignites the
COMPONENTS
The solid state module is a complete unit that includes the laminations and spark plug wire.
The spark plug is made up of two electrodes. The outside electrode is grounded and secured to the threaded sleeve. The center electrode is insulated with porcelain. The two are separated by an air gap which creates a resistance. A large voltage from the module arcs the air gap which causes a spark and ignites the
NOTE: Always consult parts manual for correct plug and reach.
1
STANDARD |
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The flywheel with magnets provide the magnetic flux (or field) which is necessary to induce voltage and trigger the module to provide spark.
The flywheel key locates the flywheel to the crankshaft in the proper position for ignition timing. If a flywheel key is sheared, or partially sheared, the engine will not start or can be difficult to start (diag. 3).
NOTE: Always replace flywheel keys by Model and Specification Number. Tecumseh has some keys that look similar but affect ignition timing.
3
TESTING PROCEDURE
1.Check for spark using a commercially available spark tester and following the tester's recommended procedure.
2.Check the spark plug for cracks in the porcelain, pitted or burned electrodes, excessive carbon buildup, and proper .030" (.762 mm) air gap setting. Replace if questionable. Try to start and run the engine. If the engine will not start or run properly proceed to step #3.
3.Attach the spark plug wire to the spark plug tester and ground the tester as in step #1. Remove the blower housing, disconnect the ignition grounding lead at the ignition module. Reinstall the blower housing and crank the engine over. If spark occurs, check the ignition switch, safety interlock switches, or electrical wiring for shorting to ground.
3/4" (19.05 mm)
MAGNETS
4
4.Check the air gap between the flywheel magnets and the laminations of the ignition module. It should be
.0125" (.3175 mm) or use gauge part # 670297.
5.Check the flywheel magnets for the proper strength using this rough test. Hold a screwdriver at the extreme end of the handle with the blade down, move the blade to within 3/4 inch (19.05 mm) of the magnets. If the screwdriver blade is attracted to the magnets, the magnetic strength is satisfactory (diag. 4).
6.Examine the ignition module and lamination assembly for cracks in insulation or other damage, which would cause shorts or leakage of current.
7.Check the operation of the ignition module using an approved tester following the instructions furnished with the test unit, or booklets offered by the Tecumseh Products Co. Engine and Transmission Group Service Division.
Ignition modules are permanently attached to the lamination and must be serviced as an assembly.
54
FOUR CYCLE IGNITION TROUBLESHOOTING
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test |
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Spark |
No Spark |
Set proper air gap on
ignition module
Test ignition module for intermittent or weak spark
Check electric starter and
battery if applicable
Equipment problem,
check switches, wiring and equipment controls
Engine problem, check for shorts or grounds in wiring
Disconnect ignition
Check for proper air gap
on ignition module
and repeat test
Check flywheel magnets
for strength
Test ignition module
55
SERVICE |
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To remove the ignition module or the flywheel from |
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GAP GAUGE |
the engine, see Chapter 9 under "Disassembly". |
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SPARK PLUG SERVICE |
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Spark plugs should be removed, cleaned, and |
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adjusted periodically. |
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adjust accordingly. Set the spark plug gap at .030" |
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anywhere. |
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NOTE: DO NOT USE A SAND BLASTER TO CLEAN PLUGS, MICROSCOPIC PARTICLES LEFT IN THE PLUG CAN SCORE THE ENGINE CYLINDER DURING OPERATION. USE A SOLVENT AND A WIRE BRUSH TO CLEAN, AND USING EYE PROTECTION, BLOW OUT THOROUGHLY WITH COMPRESSED AIR.
When replacing a spark plug consult the parts breakdown for the correct spark plug to be used in the engine being serviced.
Install the spark plug in the engine and tighten it to 180 inch pounds (20.5 Nm) torque. If a torque wrench is not available, screw the spark plug in as far as possible by hand, and use a spark plug wrench to turn the spark plug 1/8 to 1/4 of a turn further if using the old spark plug, or 1/2 of a turn further if using a new spark plug.
CONDITIONS CAUSING FREQUENT SPARK PLUG FOULING
1.Carburetor setting is too rich or the air cleaner is restricted.
2.Partially closed choke shutter.
3.Poor grade of gasoline.
4.Improper fuel.
5.Restricted exhaust system.
6.Incorrect spark plug.
7.Incorrect spark plug gap.
8.Oil level is too high, or the breather is restricted.
9.Faulty piston rings.
10.Weak ignition system.
Normal |
Carbon Deposit |
Worn |
Oil Deposit |
6 |
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56
IGNITION TIMING CHECK
In order for an engine to run effectively and efficiently, the spark must ignite the compressed
Timing on a solid state module is not adjustable. The air gap check consists of having the proper .0125" (.3175 mm) air gap gauge, part # 670297 between the flywheel magnets and the laminations of the module while tightening the mounting screws to the proper torque. Remove the air gap gauge and rotate the flywheel to check for any possible striking points. If none are found, the air gap is set correctly and the air gap check is completed (diag. 7).
.0125"
(.3175 mm)
7
SERVICE TIPS
DO NOT:
Interchange flywheels, flywheel keys, or spark plugs.
Use flywheels with cooling fins that are broken off.
Use a standard business card as an air gap gauge.
Attempt to reglue the spark plug lead back into a solid state module.
Store a solid state module within 20 feet (6.1 meters) of an unshielded welder.
57
CHAPTER 9 INTERNAL ENGINE AND CYLINDER
GENERAL INFORMATION
This chapter covers the cylinder block, piston and rod assemblies, cylinder head, crankshaft, camshaft, valve train, breather, cylinder cover, flywheel, counterbalance systems, and lubrication systems. The governors and the governor systems are covered in Chapter 4.
All Tecumseh engines covered in this manual are four cycle engines with the valves in the engine head. The crankshaft position is designated as either horizontal or vertical as the engine rests on its base. The engines identified by decals or model as XL (Extra Life) or XL/C (Extra Life / Commercial ) are made using aluminum alloy diecast around a cast iron cylinder liner. However, not all engines with cast iron cylinder liners are identified as XL or XL/C.
OPERATION
All
The engine camshaft gear is twice as large as the mating gear on the crankshaft to allow proper engine valve timing for each cycle. The crankshaft makes two revolutions for every camshaft revolution.
1.INTAKE. The intake valve is open and the exhaust valve is closed. The piston is traveling downward creating a low pressure area, drawing the
2.COMPRESSION. As the piston reaches Bottom Dead Center (BDC) the intake valve closes. The piston then rises, compressing the
3.POWER. During this piston stroke both valves remain closed. As the piston reaches the Before Top Dead Center (BTDC) ignition point, the spark plug fires, igniting the
4.EXHAUST. The exhaust valve opens. As the piston starts to the top of the cylinder, the exhaust gases are forced out (diag. 4).
After the piston reaches Top Dead Center (TDC), the four cycle process will begin again as the piston moves downward and the intake valve opens.
1
2
3
4
58
LUBRICATION SYSTEMS
The lubrication system used with all Tecumseh horizontal crankshaft engines covered in this manual utilize a splash type system. An oil dipper on the connecting rod splashes oil in the crankcase to lubricate all internal moving parts. The oil dipper is either bolted on or may be cast on to the cap with one of the rod bolts (diag. 6).
All vertical shaft engines use a positive displacement plunger oil pump or a rotary oil pump. Oil is pumped from the bottom of the crankcase, up through the camshaft and over to the top main bearing. Oil under pressure lubricates the top crankshaft main bearing and camshaft upper bearing (diag. 7). A crankshaft drilling also provides oil to the crankpin journal on engine models OHV 13.5
On all Tecumseh vertical shaft
The plunger style oil pump is located on an eccentric on the camshaft. As the camshaft rotates, the eccentric moves the barrel back and forth on the plunger forcing oil through the hole in the center of the camshaft. The ball on the end of the plunger is anchored in a recess in the cylinder flange (diag. 8).
The rotary pump is driven by the camshaft. It uses a lobed gear in a rotating ring to provide positive oil displacement (diag. 9).
SPRAY
MIST HOLE
OIL DRAIN
HOLE
5
COUNTERBALANCE SYSTEMS
Some Tecumseh engines may be equipped with an
A dual shaft counterbalance is also used on some engine models. A gear on the crankshaft drives the counterbalance with the thicker gear, which in turn drives the second counter balance shaft. For timing of either counterbalance system, see " Engine Assembly Procedure " in the Service section of this chapter.
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PUMP |
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WITH INSIDE CHAMFER
TOWARD CAMSHAFT GEAR
FLAT |
8 |
NOTE: INSTALL OIL PUMP AFTER THE SUMP IS ON 9
DRIVE
GEARCOUNTER- 
BALANCE
SHAFT
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CAMSHAFT |
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59
COMPONENTS
The cylinder block houses the piston, crankshaft, and along with the cylinder cover all the internal components. The block is a one piece diecast aluminum alloy cylinder casting which may have a cast iron liner (diag. 10).
The piston transmits the force of the burning and expanding gases through the connecting rod to the crankshaft.
The piston rings provide the seal between the cylinder wall and the piston. The rings keep the combustion pressures from entering the crankcase and also wipe the oil off the cylinder wall and return it to the sump.
The connecting rod assembly is the link between the piston (piston pin) and the crankshaft.
The cylinder head is a one piece aluminum alloy casting that is bolted to the top of the cylinder block. The overhead design contains all of the valve train except for the camshaft, lifters, and push rods.
The crankshaft converts the up and down piston movement to the rotational force (torque) by an offset crankpin or rod journal.
The camshaft lobes push the lifters at the proper time to allow air and fuel in and exhaust out of the cylinder. Teeth on the camshaft gear time the camshaft to the crankshaft.
The valves allow
The valve springs return the valves to the closed position and must be strong enough to maintain valve lifter and cam lobe contact. The valve retainers lock the spring to the valve stem.
The valve lifters maintain contact on the camshaft, move the push rods to pivot the rocker arms and move the valves.
The crankcase breather is a one way check valve that allows air out and prevents air from coming in. It allows the engine to develop a partial vacuum in the crankcase during operation.
The cylinder cover provides the bearing surface for the power take off (P.T.O.) end of the crankshaft and camshaft. This bolted on cover is removed to provide access to all internal components.
The oil pump (vertical shaft only) consists of a steel plunger and a nylon or aluminum housing that rides an offset on the camshaft. The rotary pump consists of a lobed gear in a rotating ring that is driven by the camshaft.
The flywheel provides the mass to smooth the effects of one power stroke every other crankshaft revolution. Flywheels are made of aluminum alloy or cast iron. The flywheel fins act as a fan to cool the engine.
CHAMPFER UP |
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SHAFT |
ROTOR
OIL SEAL
REMOVED
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PUSH ROD |
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RING |
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SNAP RING |
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VALVES
CRANKCASE BREATHER
CRANKSHAFT
FLYWHEEL10
60
ENGINE OPERATION PROBLEMS
ENGINE KNOCKS
Associated equipment loose or
improperly adjusted
Check for excessive carbon in
combustion chamber
Loose flywheel examine key, key way
and proper flywheel nut torque
Ignition timing or
incorrect spark plug
Loose or worn connecting rod
Worn cylinder
OVERHEATS
Excessive engine loading
Low oil level or wrong viscosity oil
Cooling air flow obstructed or clogged
cooling fins
Carburetor improperly adjusted or
improper RPM setting*
Ignition timing or
incorrect spark plug
Carbon in the combustion chamber
SURGES OR RUNS UNEVENLY
Fuel cap vent obstructed
Dirty carburetor or air filter
Carburetor improperly adjusted
Governor sticking, binding or improper
RPM setting
Carburetor linkage, shafts or shutters
sticking or binding
Intermittent spark, check ignition or
incorrect spark plug
EXCESSIVE OIL CONSUMPTION
Oil level above full
Wrong viscosity oil
Excessive engine speed
Engine cooling fins dirty causing
overheating
Breather damaged, dirty or improperly
installed
Lean carb setting causing overheating
(adjustable carb)
Piston rings worn
Worn or glazed cylinder
Valve guides worn excessively
Damaged gaskets, seals or "O" rings
61
ENGINE OPERATION PROBLEMS
ENGINE MISFIRES
Carburetor improperly adjusted
Wrong or fouled spark plug
Valves sticking or not seating properly
Ignition timing or
incorrect spark plug
Excessive carbon build up
Improper Valve Lash
Weak valve spring
ENGINE VIBRATES EXCESSIVELY
Bent crankshaft
Attached equipment out of balance
Loose mounting bolts
If applicable counter balance not
properly aligned
LACKS POWER
Air intake obstructed
Lack or lubrication or improper
lubrication
Carburetor improperly adjusted
Exhaust Obstructed
Improper valve lash
Loss of compression (worn rings,
blown head gasket)
BREATHER PASSING OIL
Oil level too high
Excessive RPM or improper governor
setting
Damaged gaskets, seals or "O" rings
Breather damaged, dirty or improperly
installed
Piston rings not properly seated or ring
end gaps are aligned
Angle of operation too severe
62
TESTING
ENGINE KNOCKS
1.Check the blade hub, blade adapter, or crankshaft coupler for loose fit, loose bolts, or crankshaft key damage. Remove, inspect, replace if necessary. Reinstall and
2.Check the flywheel key and the flywheel and crankshaft keyway for wear or partial shearing. Replace if any damage is evident. Tighten the flywheel nut to the proper torque.
3.Check for the correct ignition module air gap.
4.Remove the cylinder head and check for excessive carbon in the combustion chamber. Also check that the head gasket fit is correct, and the spark plug for proper reach and heat range (correct spark plug for the engine).
5.Check for the proper valve lash using a feeler gauge.
6.Check the internal components (piston, cylinder, connecting rod, crankshaft journal) for excessive clearance. See Chapter 10 under "Specifications".
ENGINE OVERHEATS
1.Make sure the engine is not being overloaded. Remove excess load (sharpen blades, limit operation speed, process less material).
2.Check the oil level and viscosity. Add or replace as necessary.
3.Check for clogged cooling fins or obstructions to the air flow. Remove the blower housing, clean and reinstall.
4.Check the carburetor for correct adjustment or remove and clean the carburetor using tag wire and compressed air. See Chapter 3 under "Service."
5.Check the engine R.P.M. setting using a vibratach or other tachometer and compare it to the R.P.M. settings found on microfiche card #30 according to the engine model and specification number. Adjust as necessary.
6.Check the ignition timing. See Chapter 8 "Ignition - Service."
7.Remove the cylinder head to check for excessive carbon buildup or a leaking head gasket. Clean or replace as necessary.
SURGES or RUNS UNEVENLY
1.Check the fuel cap to make sure it is venting. Loosen the cap and retry engine operation.
2.Replace or clean the air filter.
3.Check the carburetor adjustment or clean the carburetor. See Chapter 3 under "Service."
4.Check the engine R.P.M. setting using a vibratach or other tachometer and compare it to the R.P.M. settings found on microfiche card # 30 according to the engine model and specification number. Adjust as necessary.
5.Visually check all linkages. Check the governor shaft, throttle shaft, or pivot points for binding.
6.Check the ignition module operation using a gap type tester installed between the high tension lead and spark plug. Check for intermittent spark.
ENGINE MISFIRES
1.Check the spark plug for the proper application or a fouled condition. Replace if questionable.
2.Reset the carburetor following the adjustment procedure or clean the carburetor. See Chapter 3 under "Service."
3.Check the ignition timing. See Chapter 8 under "Service."
4.Check for carbon buildup in the combustion chamber.
5.Check valve lash. Inspect the valves and valve seats for leakage. Check for scoring or discoloration on the valve stem in the valve guide area. Recut the valves and seats if questionable. See "Valve Service" in this chapter.
63
ENGINE VIBRATES EXCESSIVELY
1.Remove the spark plug wire. Check the engine crankshaft on the PTO end for bends using a straight edge, square or a dial indicator. Blades or adapters must be removed. Significant deflection will cause a vibration problem.
2.Check the engine mounting bolts, make sure they are tight.
3.Remove and check the attached equipment for an out of balance condition.
4.If the engine is equipped with a counterbalance shaft, check the gear timing to determine if the counterbalance is out of time.
BREATHER PASSING OIL
1.Check the oil level, make sure the engine is not overfilled. Also verify that the viscosity rating on the container of the oil being used is to specification.
2.Check the angle of operation. Avoid prolonged use at a severe angle.
3.Check the engine R.P.M. setting for excessive R.P.M. using a vibratach or other tachometer and compare it to the R.P.M. settings found on microfiche card # 30 according to the engine model and specification number. Adjust the high and low R.P.M. as necessary.
4.Check for leaking or damaged gaskets, seals, or
5.Check the breather for damage, dirty condition, or improper installation. The oil return hole(s) must face down.
6.Check the engine compression using a compression tester. If the engine has weak compression, determine the cause of weak compression: worn rings, leaking head gasket, or leaking valves. Follow the compression tester's procedure.
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NOTE: MICROFICHE CARD 30 RPM'S ARE NOT ON PAPER
NOTE: RPM SETTINGS CAN ALSO BE FOUND ON THE COMPUTERIZED PARTS LOOK UP SYSTEMS.
11
EXCESSIVE OIL CONSUMPTION
1.Check the oil level, oil viscosity on the container of the oil being used, and oil condition. Replace and fill to the proper level.
2.Check the angle of operation. Avoid prolonged use at a severe angle.
3.Check for leaking or damaged gaskets, seals, or
4.Check the engine R.P.M. setting using a vibratach or other tachometer and compare it to the R.P.M. settings found on microfiche card # 30 according to the engine model and specification number. Adjust as necessary. The computer parts lookup systems also have RPM information listed in each individual engine parts list.
5.Check the breather for damage, dirty condition, or improper installation. The oil return hole(s) must face down.
6.Clean the cooling fins to prevent overheating.
7.Check the carburetor setting causing a lean running condition, overheating the engine.
8.Check the engine compression using a compression tester. If the engine has weak compression, determine the cause of weak compression: worn rings, leaking head gasket, or leaking valves. Follow the compression tester's procedure.
9.Check the valve guide clearance for excessive wear.
64
LACKS POWER
1.Check the air intake for an obstruction (dirty filter, oil saturated filter, other debris).
2.Check the oil level, oil viscosity on the container of the oil being used and oil condition. Replace and fill to the proper level.
3.Readjust the carburetor or remove the carburetor for cleaning. See Chapter 3 under "Service."
4.Check the exhaust port or muffler for a restriction preventing proper exhaust flow.
5.Check the engine valve lash. Reset the valves at the proper lash.
6.Check the valves for proper seating and valve guide clearance. Recondition the valves and seats. Replace the valves if necessary. See "Cylinder Head and Valve Train Service" in this chapter.
7.Check the ignition timing. Check the flywheel key for partial shearing.
SERVICE
DISASSEMBLY PROCEDURE
The following procedures apply to most engine models. Actual procedure may vary.
1.Disconnect the high tension lead from the spark plug. Remove the spark plug.
2.Drain the oil from the crankcase. Drain or shut off the fuel supply.
3.Remove the air cleaner assembly.
4.Remove the fuel tank if it is attached to the engine. Fuel tanks may be held on with bolts, screws, or some models require taps upward with a soft face hammer loosening the plastic tank wedges in the blower housing slots.
5.Remove the blower housing by first unscrewing the screw holding the dipstick tube to the blower housing and removing the remaining bolts holding on the blower housing.
6.Unplug the ignition kill wire from the terminal on top of the ignition module and unbolt the ignition module.
7.Locate the piston at Top Dead Center (TDC) on the compression stroke for easier valve train service.
8.Relieve the compliance brake pressure on the flywheel if applicable. Compress the spring by moving the lever toward the spark plug end and when the hole in the lever aligns with the hole in the bracket secure the lever in this position with alignment tool part # 670298.
9.Remove the flywheel nut, washer, and starter cup. Use a part # 670305 strap wrench to hold the flywheel from turning (diag. 12). Thread the appropriate flywheel
# 670169, 5/8" / 15.875 mm use part # 670314, 11/16" / 17.462 mm use part # 670329) on the crankshaft until it bottoms out, then unthread it one complete turn. Lift upward under the flywheel using a large screwdriver while avoiding contact with the alternator coils or magnets, and tap sharply and squarely on the
NOTE: DO NOT USE A JAW TYPE PULLER.
SOCKET WRENCH
FLYWHEEL
FLYWHEEL |
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TOOL |
12 |
METAL HAMMER
KNOCK OFF TOOL
SCREWDRIVER
TO RAISE
FLYWHEEL
13
14
65
10.Remove the flywheel key and alternator if equipped, and baffle plate.
11.Remove the muffler.
12.Remove the intake pipe, spacer if equipped, and the carburetor. Be careful not to bend or damage the linkage when removing. Mark the hookup points or diagram the linkage arrangement to aid in reassembly.
13.Remove the head by first removing the valve cover. The push rod guide plate must be removed to access one of the head bolts. Remove the rocker arms by loosening the two locking nuts or allen head screws. Use a 3/16" Allen wrench and a 7/16" wrench on OHH, OVRM and OHV
NOTE: ON SOME OHV ENGINES THE EXHAUST PUSH ROD CAN ONLY BE REMOVED AFTER THE HEAD IS OFF. YOU MUST HAVE IT BACK IN BEFORE RE- ASSEMBLY.
On engine models OHM, OHSK120, OVM, OVXL and OHV, with independent cylinder head and rocker box, the valve springs, caps, retainers, and retainer screw must be removed to allow the rocker box to separate from the head. Remove the jam nut, adjusting nut, rocker arm bearings, rocker arms, push rods, guide plate, and the rocker arm retainer screw.
Next to prevent valve or piston damage turn the piston down in the cylinder. Then place a 3/4" (19.05 mm) deep socket over the valve cap and strike the top with a steel hammer (diag. 15). This action loosens the cap. Remove the cap, retainers, and valve springs. Remove the rocker arm housing, head bolts, head, head gasket and valves. Notice the "O"rings used to seal the rocker box , valve stems, and push rod tubes.
14.Remove the crankcase breather if necessary.
15
66
15. Remove the cylinder cover or mounting flange |
using a seal protector positioned on the seal to |
prevent seal damage. The crankshaft must be |
free of rust or scale to slide the cover or flange |
off the crankshaft. OHH engines with a ball |
bearing on the P.T.O. end of the crankshaft |
require the oil seal and the snap ring to be |
removed prior to the cylinder cover removal. For |
engines equipped with |
turn the crankshaft to roll the reduction shaft gear |
off the crankshaft worm gear when removing the |
cylinder flange (diag. 16, 17, 18, 19). |
16. On engines equipped with |
reduction, remove the auxiliary shaft from the |
cover by removing the retaining ring and sliding |
the shaft out of the washers and drive gear. |
17. Align the timing marks on the camshaft and |
crankshaft gears and remove the internal |
components (diag. 20). |
18. Remove the lifters, rod cap, and counterbalance |
shaft or gears if applicable. |
19. Before removing the piston, remove any carbon |
from the top of the cylinder bore to prevent ring |
breakage. Push the piston out the top of the |
cylinder bore. |
20. Remove the valves from the head on models |
OHH and OVRM by supporting the valves with |
fingers while compressing the valve springs, one |
at a time, with thumbs. Slide the large opening |
in the retainer toward the valve stem to remove |
(diag. 21). On all other overhead valve engine |
models, place a 3/4" (19.05 mm) deep socket |
over the valve cap and strike the top with a steel |
hammer. This action loosens the cap. Remove |
the cap, retainers, and valve springs. The valve |
OIL SLEEVE TOOL
MOUNTING FLANGE
OIL SEAL
16
GEAR 17
WORM GEAR
18
OIL SEAL REMOVED
springs must be assembled on the same valve |
they are removed from (diag. 15). |
SNAP RING
BEVELED TOOTH
19
TIMING MARK
CRANKSHAFT |
CAMSHAFT |
20 |
GEAR |
GEAR |
21
67
CYLINDERS
Visually check the cylinder for broken or cracked fins or a scored cylinder bore. Check the main bearing for wear or scoring. If the main bearing is worn or scored it can be replaced on some models. See "Crankshaft Bearing Service" in this chapter.
Use a dial bore gauge or transfer gauge with a micrometer to accurately measure the cylinder bore. Measure in the piston travel area approximately 1/2" to 3/4"
.Measure at 90 degrees to the piston pin, 45 degrees to the piston pin, and even with the piston pin as the piston would appear when assembled. A rigid hone is recommended to "true" any cylinder irregularities. If the cylinder bore is worn more than .005" (.127 mm) oversize, out of round or scored, it should be replaced or
.010
.010
22
To recondition a cylinder, use a commercially available hone of the proper size . Chuck the hone in a drill press with a spindle speed of about 600 R.P.M. Tecumseh recommends 380 grit for finish in a standard cross hatch.
Start with coarse stones and center the cylinder under the drill press spindle. Lower the hone so the lower end of the stones contacts the lowest point in the cylinder bore.
Rotate the adjusting nut so that the stones touch the cylinder wall and begin honing at the bottom of the cylinder. A light honing oil should be used to lubricate and cool while honing. Move the hone up and down at a rate of 50 strokes per minute to avoid putting ridges in the cylinder wall. Every fourth or fifth stroke, move the hone far enough to extend the stones one inch beyond the top and bottom of the cylinder bore.
Check the bore diameter every twenty or thirty strokes for size and a 350 - 450 crosshatch pattern. If the stones collect metal, clean the stones with a wire brush when the hone is removed.
If cylinder oversizing is needed we recommend boring the cylinder. This service is offered by many Service Dealers. You also may wish to contact a local machine shop.
Clean the cylinder and crankcase with warm, soapy water, rinse with clean water, and dry thoroughly. Continue the cleaning procedure until a clean white cloth wiped on any internal surface reveals no honing residue or dirt.
Replace the piston and the piston rings with the correct oversize parts as indicated in the parts manual.
68
CYLINDER HEAD AND VALVE TRAIN SERVICE
Check the cylinder head for warpage by placing the head on a precision flat surface. If warped in excess of .005" (.127mm), replace the head. Slight warpage can be corrected by placing a sheet of #400 wet /dry sandpaper on a precision flat surface and rubbing the head gasket surface in a circular pattern until the entire gasket surface shows evidence of sanding. A small amount of honing oil on the sandpaper will make it easier to slide the head. Always replace the head gasket and torque the head bolts in 60 inch pound (6.7 Nm) increments in the numbered sequence torques in specification section (diag. 23 & 24).
Valves, Springs, And Push Rods
The valves should be checked for proper lash, sealing, and wear. Valve condition is critical for proper engine performance. Valve lash should be checked before removal of the engine head if any of the following conditions are experienced; a popping is heard through the intake or exhaust, an engine kickback is experienced, or when excessive valve train noise is heard.
Valve lash (between the rocker arm and valve stem) should be set or checked when the engine is cold. The piston should be at T.D.C. on the compression stroke (both valves closed). See specification section.
When servicing the valves, all carbon should be removed from the valve head and stem. If the valves have been checked and are in a usable condition, the valve face should be ground using a valve grinder to a 45 degree angle. If after grinding the valve face the margin is less than 1/32 of an inch (.794 mm), the valve should be replaced (diag. 25).
3
1 |
5 |
4 |
2 |
|
|
TORQUE SEQUENCE |
23 |
|
OVRM / OHH, OHSK50 - 70 |
24
5 |
1 |
|
|
3 |
6 |
|
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|
TORQUE SEQUENCE |
|
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|
24 |
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|
OHV 11 - 17, OHM, OHSK80 - 130 |
||
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MARGIN |
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1/32" |
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450 |
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(.794 mm) |
FACE |
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MINIMUM |
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DIMENSION |
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STEM |
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25
Valves are not identical. Valves marked "EX" or "X" are installed in the exhaust valve location. Valves marked "I" are installed in the intake valve location. If the valves are unmarked, the smaller valve (head) is installed in the exhaust valve location.
If the spring has dampening coils, the valve spring should be installed with the dampening coils away from the valve cap and retainers (diag. 26).
The valve springs should be checked for both ends being parallel and the free length being at least 1.105" (28.067 mm) for OHH and OVRM engines, 1.980" (50.292 mm for OHM, OVM, OHSK, OVXL, and OHV engines when the valves are removed for service. Replace the springs if necessary.
The push rods should be checked for straightness and the ends for wear. If the push rod ends are worn or damaged, inspect the corresponding rocker arm socket or valve lifter for wear. Replace if necessary.
FREE LENGTH
OVRM/OHH/
ALL OTHERS 1.980" (50.292 mm)
DAMPENING COILS LOCATED CLOSER TOGETHER
THIS END MUST FACE TOWARD THE STATIONARY PART OF THE ENGINE
(CYLINDER HEAD)
26
69
PISTONS, RINGS, AND CONNECTING RODS
Piston
The piston should be checked for wear by measuring near the bottom of the skirt 90 degrees from the piston pin hole with a micrometer. Check the ring side clearance using a feeler gauge with a new ring. Clean all carbon from the piston top and the ring grooves before measuring. Visually inspect the piston skirt area for scoring or scratches from dirt ingestion. If scoring or deep scratches are evident, replace the piston.
If the cylinder bore needs
Piston Rings
After the cylinder bore diameter has been checked and is acceptable to rebuild, the ring end gap should be checked using new rings. Place a new compression ring squarely in the center of the ring travel area. Use the piston upside down to push the ring down (diag.
28)and measure the gap with a feeler gauge. The ring end gap must be within the specification to have adequate oil control (diag. 29). This procedure will assure correct piston ring end gap measurement. Ring side clearance should also be checked with a feeler gauge when using new rings with an old piston (diag.
30).
Replace the rings in sets and install the piston, rings, and rod assembly in the cylinder bore with the ring end gaps staggered. When installing new rings in a used cylinder, the cylinder wall should be
Use a ring expander to remove and replace the rings. Do not spread the rings too wide or breakage will result.
Piston Ring Orientation
If the top compression ring has an inside chamfer, this chamfer must face UP. The second compression ring will have either an inside chamfer or an outside notch. The rule to follow is an inside chamfer always faces up. An outside notch (diag. 31) will face down or towards the skirt of the piston.
The oil control ring can be installed with either side up. The expander (if equipped) end gap and the ring end gap should be staggered (diag. 31).
NOTE: Always stagger the ring end gaps on re- assembly.
INDICATES
.010" (.254 mm) OVERSIZE PISTON
PISTON MEASUREMENTS ARE TAKEN AT |
|
BOTTOM OF SKIRT 900 FROM WRIST PIN HOLE |
27 |
CYLINDERPISTON
PISTON RING
28
29
CHAMFER
1ST COMPRESSION RING
2ND COMPRESSION RING
3RD OIL CONTROL RING
30
EMISSION RINGS
1ST COMPRESSION RING
2ND COMPRESSION RING
3RD OIL CONTROL RING
31
70
CONNECTING RODS
Some engine models have offset piston pins (not centered) to centralize the combustion force on the piston. When installing the connecting rod to the piston it is imperative that the rod be installed correctly. On engine models OVM, OHM, OHSK120 - 130, and OVXL, the piston will have an arrow stamped on the top of the piston. On OHV 13.5 - 17 engines, an arrow is found on the piston skirt. The arrow on the top of piston or on the piston skirt must point toward the push rods or the carburetor side of the engine when installing it in the cylinder. (diag. 32) If the piston does not have an arrow, the piston can be installed either direction on the connecting rod. On all engine models, the match marks on the connecting rod and cap must align and face out when installing the piston assembly into the engine (diag. 33 & 34).
On horizontal shaft engines, oil dippers are attached to the bottom connecting rod bolt. Some engines have the oil dipper cast in the rod cap. Consult the specification chart for the proper rod bolt torque when installing the cap. The rod bolts should be torqued in 50 inch pound (5.65 Nm) increments until the specified torque is achieved.
CRANKSHAFTS AND CAMSHAFTS
ARROW DIRECTION
32
MATCH MARKS
MATCH
MARKS
33 |
34 |
BEVEL
CHAMFER TOOTH
CRANKSHAFT GEAR
Inspect the crankshaft visually and with a micrometer for wear, scratching, scoring, or out of round condition at the bearing surfaces. Check for bends on the P.T.O. end using a straight edge, square or a dial indicator.
CAUTION: NEVER TRY TO STRAIGHTEN A BENT CRANKSHAFT.
The timing marks on the camshaft and the crankshaft gears must be aligned for proper valve timing. (diag. 35 & 36).
Camshafts
Check the camshaft bearing surfaces for wear using a micrometer. Inspect the cam lobes for scoring or excessive wear. If a damaged camshaft is replaced, the mating crankshaft and governor gear should also be replaced. If the crankshaft gear is pressed on it is not serviceable and the crankshaft must also be replaced.
CAMSHAFT
GEAR TIMING
MARK
GEAR
KEYWAY
CAMSHAFT
GEAR
PUNCH
MARK
SMALL HOBBING HOLE
35
CRANKSHAFT
SMALL HOBBING HOLE
36
Clean the camshaft with solvent and blow all parts and passages dry with compressed air, making sure that the pins and counterweights are operating freely and smoothly on mechanical compression relief types.
OHH and OHSK50 - 70 engines use serviceable MCR components and must be assembled as illustrated in "Assembly" with a thrust washer placed on the camshaft next to the compression release weight.
NOTE: Some OHH models used on chipper/ shredders may not require a compression release.
COMPRESSION RELEASE MECHANISM
37
71
Mechanical Compression Release (MCR) camshafts have a pin located in the camshaft, that extends above the intake or exhaust cam lobe, to lift the valve to relieve the engine compression for easier cranking. When the engine starts, centrifugal force moves the weight outward and the pin will drop back down. The engine will now run at full compression (diag. 38).
Some OHH engines use a composite camshaft. This camshaft is used on OHH/OHSK
NOTE: You must install the thrust washer between the cover and cam to prevent wear.
Some OVRM engines use a ramp compression release (RCR) system that works with the intake valve. The ramp is located on the backside of the intake cam lobe. The ramp delays the intake valve closure, resulting in lower emissions and reduced compression for easier pull starting (diag. 39).
Valve Seats
Valve seats are not replaceable. If they are burned, pitted, or distorted they can be regrounded using a grinding stone or a valve seat cutting tool. Valve seats are ground to an angle of 46 degrees to a width of 3/64" (1.91 mm).
CAMSHAFT |
COMPRESSION |
|
|
COMPRESSION |
RELEASE SPRING |
RELEASE |
|
|
THRUST |
|
WASHER |
|
A |
INSERT |
|
SPRING |
|
END "A" |
|
|
B |
|
38 |
INTAKE |
|
EXHAUST |
39 |
The recommended procedure to properly cut a valve seat is to use the Neway Valve Cutting System, which consists of three different cutters. OVRM and OHH engines have a small combustion chamber and require the use of a special Neway cutter #103 for the 46 and 31 degree combination cutter. The 60 degree cutter is Neway cutter # 111. The tapered pilots required are; Neway #
First, use the 60 degree cutter to clean and narrow the seat from the bottom to the center (diag. 40). Second, use the 31 degree cutter to clean and narrow the seat from the top toward the center (diag. 41).
Third, use the 46 degree cutter to cut the seat to a width of 3/64" (1.191 mm) (diag. 42). Check the contact area of a new or reconditioned valve face on a finished valve seat. Using fingers, snap the valve sharply against the corresponding valve seat and view the line imprinted on the valve face. The contact area or line should be continuous and appear on the upper 1/3 of the valve face.
BOTTOM |
|
|
NARROWING |
|
460 |
CUTTER |
TOP NARROWING |
|
|
CUTTER |
310 |
|
150 |
|
|
600 |
|
|
SEAT |
|
|
SEAT |
|
BOTTOM |
|
|
NARROWING |
40 |
41 |
TOP |
SEAT CUTTER |
310 |
NARROW |
|
|
460 |
3/64" SEAT |
|
BOTTOM |
|
NARROW |
42 |
|
72
VALVE LIFTERS
When removing the lifters, mark the lifters to install the lifter in the same position as it was removed from. The valve lifters may be slightly different lengths. Visually check the lifter for wear on the cam contact surface and push rod contact surface.
VALVE GUIDES
Engine models OVM, OHM, OHSK80 - 130, and OVXL have valve guides that can be reamed 1/32" (.794 mm) oversize or be replaced as service parts. All other overhead valve engines have valve guides that are permanently installed in the cylinder head. If the guides get worn excessively, they can be reamed oversize to accommodate a 1/32" (.794 mm) oversize valve stem.
The guides should be reamed oversize with a straight shanked hand reamer or low speed drill press. Refer to the "Table of Specifications" (Chapter 10) to determine the correct oversize dimension. Reamers are available through your local Tecumseh parts supplier. Consult the tool section in Chapter 11 for the correct part numbers.
The upper and lower valve spring caps must be redrilled to accommodate the oversize valve stems. After oversizing the valve guides, the valve seats must be recut to align the valve seat to the valve guide.
VALVE GUIDE REMOVAL (WHERE APPLICABLE, CONSULT PARTS MANUAL)
1.Submerge the head in a container of oil so that both guides are completely covered with oil.
2.Heat the oil on a hot plate approximately 15- 20 minutes until the oil begins to smoke. Oil temperature must be 375o - 400oF (1900 - 2040C).
CAUTION : USE PROTECTION FOR EYES AND HANDS, BE CAREFUL ! THE HOT OIL AND HEAD CAN EASILY CAUSE BURNS.
3.Using a pliers, remove the head from pan of oil. Carefully drain the excess oil out of the head. Quickly work the next two steps while the head is hot to prevent pressing the guides out with the head too cool. Guides removed too cool will permanently damage the head by removing aluminum necessary to hold the new guides in place.
GUIDES
HEAD
OIL
HOT PLATE
HEAT UNTIL OIL BEGINS TO SMOKE |
43 |
4.Place the head on the bed of an arbor press on parallels with the snap rings on the long ends of the guides facing down.
5.Using a 1/2" (12.7 mm) diameter, 6" (15.24 cm) drift punch located in the center of the old valve guide, push the guide out of the head with the arbor press. Do not allow the drift punch to contact the head during this step.
VALVE GUIDE INSTALLATION
1.Install the snap rings on the new replacement valve guides. Place the valve guides in a freezer for an hour or longer to ease assembly.
2.Submerge the head in a container of oil so that the valve guide bores are completely covered with oil. Heat the container on a hot plate approximately
CAUTION : USE PROTECTION FOR EYES AND HANDS, BE CAREFUL ! THE HOT OIL AND HEAD CAN EASILY CAUSE BURNS.
3.Using a pliers, remove the head from pan of oil. Carefully drain the excess oil out of the head. Quickly work the next two steps while the head is hot to prevent damage to the guides or the head.
4.Place the head on a 6" x 12" (15.24 x 30.5 cm) piece of wood with the head gasket surface down.
5.Insert the new guides in the head with the long end of the guides up. It may be necessary to use a rubber or rawhide mallet to fully seat the new guide to the snap ring.
NOTE: DO NOT USE A STEEL HAMMER TO SEAT THE NEW GUIDE, GUIDE OR HEAD DAMAGE WILL RESULT.
6.Allow the head to cool and
73
CRANKCASE BREATHERS
The breather element and case can be cleaned using cleaning solvent. Make sure the small drain hole or holes are clean and installed down to allow return of oil back into the crankcase.
Top Mounted Breather
This type of breather is mounted in the top and rear of the cylinder block in vertical shaft engines. The umbrella check valve allows positive pressure to be vented through the element and out the tube. Most engines have the breather tube connected to the air cleaner assembly (diag. 44).
Late production OVRM engines use the rubber boot and breather tube as a "pop in" design. Mark or note the location of the breather tube. Use a large flat blade screwdriver to pry the boot up and lift the breather assembly out. Be careful not to drop the breather body out of the rubber boot when removing (diag. 45).
A new breather tube boot is recommended for replacement to assure proper crankcase seal. Apply engine oil to the breather tube boot and push the breather in until the top shoulder of the boot contacts the crankcase.
OHH engines use an umbrella valve type breather that is found in the rocker arm cover. Use solvent and compressed air to clean the area if necessary. Individual components are serviced only by the replacement of the complete cover.
TUBE
ELEMENT |
CHECK VALVE |
|
|
BAFFLE |
|
OIL RETURN |
PRESSURE OUT |
|
44
45
Side Mounted Breather
This type of breather mounts over the valve compartment and uses a reed style check valve. Clean the internal element or reed area with solvent and compressed air if necessary. When installing, the drain holes must be open and be on the bottom.
On OHV13.5 - 17 engines, align the reed valve and plate parallel to the top surface of the breather opening in the crankcase. If the plate has a notched corner, install the notch toward the P.T.O. side of the engine. If the plate is marked, install the plate with the mark facing out. Hold the reed valve and plate in this position while tightening the screw.
GASKET
COVER
BODY REED
DRAIN
HOLE
46
BODY
FILTER
GASKET
COVER TUBE
47
2 |
1 |
4 |
5 |
3 |
1 - Valve, Reed |
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2 |
- Plate, Limit |
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3 - Screw |
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4 |
- Baffle/Gasket |
48 |
|
5 - Cover |
||
BREATHER OUTLET
TO CARB
UMBRELLA
49
74
CYLINDER COVER, OIL SEAL, AND BEARING SERVICE
The following procedures, except oil seal replacement, require the engine to be disassembled. See "Engine Disassembly Procedure" in this chapter.
Cylinder Cover
Clean and inspect the cover, looking for wear and scoring of the bearing surfaces. Measure the bearing surface diameters using a micrometer and check the specifications for worn or damaged parts. Replace as necessary.
When reinstalling the cover, apply a drop of Loctite 242 to the cover screw threads and torque the cover screws to the recommended specification. Always use new gaskets and new oil seals installed using seal protectors after the cover is removed.
Oil Seal Service
NOTE: BEFORE REMOVING THE OIL SEAL, CHECK TO SEE IF THE SEAL IS RAISED OR RECESSED. WHEN INSTALLING A NEW OIL SEAL, TAP IT INTO POSITION GENTLY UNTIL IT IS SEATED INTO ITS BOSS. SOME SEALS ARE NOT POSITIONED FLUSH TO THE CYLINDER COVER. ATTEMPTING TO INSTALL THE SEAL TOO FAR IN CAN CAUSE DAMAGE TO THE OIL SEAL AND ENGINE.
If the crankshaft is removed from the engine, remove the old oil seals by tapping them out with a screwdriver or punch from the inside. If the crankshaft is in place, remove the seal by using the proper oil seal puller (diag. 50).
Select the proper seal protector and driver from the tool list in Chapter 11 to install a new oil seal. Place the oil seal over the protector and place it over the crankshaft. Drive the seal into position using the universal driver part no. 670272. The seal protector will insure that the seal is driven in to the proper depth (diag. 51).
CRANKSHAFT BEARING SERVICE Ball Bearing Service
Remove the two bearing retainer screws and washers. Remove the ball bearing in the cylinder cover by pressing the bearing from the outside of the cover toward the inside using an arbor press.
Install a new ball bearing by pressing the bearing from the inside of the cover toward the outside until the bearing contacts the shoulder. Install the two bearing retainer screws with washers and tighten to 45 in. lbs. (5.0 Nm) of torque.
OIL SEAL REMOVER TOOL: POSITIONED FOR REMOVAL OF OIL SEAL
OIL SEAL
50
|
OIL SEAL |
|
DRIVER 670272 |
OIL SEAL |
OIL SEAL |
|
DRIVER |
|
PROTECTOR |
51
OIL SEAL REMOVED
SNAP RING
52
75
SERVICE BUSHING
We are supplying this bushing for service repair. After the bushing has been installed, it requires line reaming to the proper size.
Following the chart below, have a reputable machine shop do this work for you.
|
BUSHING SIZE CHART |
|
BUSHING SERVICE |
FINISHED REAM |
|
PART NUMBER |
BORE DIAMETER |
|
30979 |
.8755 |
|
31461 |
1.0000 |
- 1.0005" (25.4 - 25.413 mm) |
31462 |
1.0000 |
- 1.0005" (25.4 - 25.413 mm) |
31546 |
1.0000 |
- 1.0005" (25.4 - 25.413 mm) |
33368 |
1.1880 |
- 1.1890" (30.175 - 30.2 mm) |
34836 |
1.0005 |
- 1.0010" (25.413 - 25.425 mm) |
34837 |
1.0005 |
- 1.0010" (25.413 - 25.425 mm) |
35377 |
1.3765 |
- 1.3770" (34.950 - 34.976 mm) |
35400 |
1.3765 |
- 1.3770" (34.950 - 34.976 mm) |
ENGINE ASSEMBLY
The following procedures apply to most engine models. Actual procedure may vary.
1.Use new gaskets and seals at all locations. Clean all internal engine parts with solvent and blow dry with compressed air or allow to dry.
2.Using the correct seal protector (see Chapter 11 under "Tools"), apply engine oil to the crankshaft bearing surfaces and insert the tapered end of the crankshaft in the crankcase. Slide the crankshaft in until it bottoms.
3.Apply engine oil to the piston skirt, rings, connecting rod bearing surface, and the cylinder bore. Using a band type ring compressor, stagger the ring end gaps, compress the rings, and push the piston assembly into the cylinder with the match marks on the connecting rod facing out of the crankcase and the arrow on the top of piston or on the piston skirt pointing toward the push rod location or the carburetor side of the engine if applicable. Push the piston assembly in until the rod is positioned on the crankshaft rod journal surface.
4.Align the match marks on the rod cap and rod, install the rod cap bolts and dipper if applicable and tighten the bolts in equal increments to the specified torque.
OIL SEAL
PROTECTOR
53
MATCH MARKS
DURLOCK BOLT
54
76
5.Assemble the compression release components to the camshaft on engine models OHH and
NOTE: Some OHH models used on chipper/ shredders may not require compression release mechanisms.
6.Some OHV11 - 17 engines come equipped with a spin on oil filtration system. If the engine is not equipped with a filter, one may be added
IF THE SUMP HAS AN OIL PASSAGE COVER. The kit part number 36435A should be ordered to upgrade the engine if desired.
7.Install the lifters, camshaft, barrel and plunger style oil pump (chamfered side toward the gear) if applicable,
DRIVE GEAR,
CRANKSHAFT
|
MATCH MARK |
|
THINNER |
THICKER |
|
GEAR |
||
GEAR |
||
|
DUAL SHAFT
COUNTERBALANCE
a.Dual Balance Shaft
Time the dual shaft counterbalance system with the piston at T.D.C. Install the counterbalance with the thicker gear in the far right boss in the crankcase and the other counterbalance shaft with the thinner gear in the far left boss while aligning the timing marks. Slide the drive gear over the keyway in the crankshaft while aligning the timing mark with the thicker counterbalance gear.
NOTE: Engines equipped with rotary oil pumps must have the drive shaft and pump assembled after the sump cover is installed.
COMPRESSION |
CAMSHAFT |
COMPRESSION |
|
RELEASE |
RELEASE SPRING |
|
THRUST |
|
WASHER |
|
A |
|
INSERT |
|
SPRING |
|
END "A" |
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B |
|
55 |
|
GASKET |
OIL PASSAGE GASKET
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SCREW |
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OIL PUMP |
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OIL |
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SHAFT |
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OIL PUMP ASSY. |
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PASSAGE |
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"O" RING |
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COVER |
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OIL PUMP COVER |
56 |
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CHAMPFER UP
TOWARD CAM
57
CAM TIMING
58
TIMING
59
77
8.Mount the cylinder cover or flange with the governor gear assembly installed to the crankcase using dowel pins to position the cover and a new gasket. Install the cover down onto the crankcase and slightly rotate the crankshaft to allow the governor gear to mesh. Do not force. Apply a drop of blue Loctite 242 to the cover screw threads and tighten to the specified torque.
On engines with ball bearings in the cover, install a thrust washer (if applicable) over the crankshaft, followed by the retaining ring.
On OHV 13.5
9.Install the breather assembly.
10.Rotate the crankshaft to place the piston at Top Dead Center (TDC) on the compression stroke.
NOTE: Always cut the valve seats, never only lap the seats.
11.
For OHV models, place the springs (dampening coils toward the head) over the valve guide and place the valve caps on the springs with the larger opening away from the springs. Use spring compressor tool part # 670315A installed on a rocker arm stud, and either turn the stud in or secure with a locking nut as shown so about
Install the cylinder head using a new head gasket. On OHV
NOTE: Tecumseh strongly recommends you order a complete seal kit. Replace all "O" ring and gaskets in kit.
SHAFT
ROTOR
RING |
ROTARY PUMP |
60 |
|
NOTE: INSTALL OIL PUMP AFTER THE SUMP IS ON 61
62
RETAINERS HELD BY SPRING
TENSION AGAINST THE CAP
RETAINER
CAP
VALVE SPRING
COMPRESSOR TOOL
PART NO. 670315
63
78
12.STEPS 12A
a.Install the push rods with the cupped ends of the rods placed on top of the lifters. Visually check correct placement through the valve box opening. Use lubricated new "O" ring seals for both ends of the push rod tubes and install the push rod tubes in the crankcase.
b.Install the valves into the head, and using a new head gasket, place the head on the cylinder block. Tighten the head bolts in the numbered sequence using 60 inch pound (6.8 Nm) increments to the specified torque.
c.Install the rocker arm housing, push rod guide plate with the legs facing up, new rocker arm studs with "O" rings under the guide plate. Install the valve box to head retaining screw using a flat washer and a new "O" ring. Tighten the screw and the studs to the specified torque.
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DAMPENING COILS |
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LOCATED CLOSER |
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TOGETHER |
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THIS END MUST FACE |
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FREE LENGTH |
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1.980" (50.292 mm) |
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TOWARD THE |
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ALL OTHERS |
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STATIONARY PART |
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OF THE ENGINE |
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(CYLINDER HEAD) |
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OVRM/OHH 1.105 (28.067 mm) |
64 |
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(BLACK) |
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TEFLON EXHAUST |
"O" RINGS |
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(WHITE) |
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OVM / OHM STYLE |
65 |
d. Lift each valve up until it contacts the seat and hold the valve in this position. Use a 12 inch (30.5 cm) piece of fuel line and wedge one end on each side of the valve stem through the port opening to hold the valve.
e. Bolt the valve spring compressor tool part
# 670315A on a rocker arm stud using the rocker arm bearing and locking nut (diag. 66).
f.Install the new
g.Compress the valve spring with the tool and insert the two retainers into the keeper so the inside ridge of the retainer locks into the valve stem groove. Repeat the procedure for the other valve (diag. 66).
NOTE: TORQUE THE CYLINDER HEAD FOLLOWING THE SEQUENCE ON PAGE 69.
RETAINERS HELD BY SPRING
TENSION AGAINST THE CAP
RETAINER
CAP 
VALVE SPRING
COMPRESSOR TOOL
PART NO. 670315
66
79
13.On engine models OHH and OVRM, install the push rods on the lifters, and rocker arms and lock nuts on the rocker arm pivot screws. Fasten the screw to the head with the push rod guide plate tabs facing up. Turn the screws in until slight play exists between the valve stem and rocker arm.
On OHM, OHSK120, OVM, and OVXL models, install the rocker arms, rocker arm bearings, and new rocker arm adjusting nuts on the studs. Tighten the adjusting nut until slight play exists.
On OHV
On OHV13.5
14.Set the valve lash with the engine cold, the piston at T.D.C., and both valves closed. Insert the specified feeler gauge between the rocker arm and valve stem. Adjust until a slight sliding drag is felt.
On models OHH and OVRM, lock this position by holding an 3/16" Allen wrench on the pivot ball screw while tightening the lock nut to 120 in. lbs. (13.5 Nm) of torque. A 7/16" crowfoot will be needed to torque the lock nut. Rotate the crankshaft at least one full turn to check push rod movement and valve lash (diag. 67).
On models OVM, OHM, OHSK120 and OVXL, with a 1/2" crowfoot, tighten down the rocker arm studs to 190 in. lbs. (21.5 Nm). Adjust the rocker arm hex nut with a 1/2" wrench to set the correct valve lash and tighten the locking jam nut to 18 in. lbs. (2 Nm). Rotate the crankshaft at least one full turn to check push rod movement and valve lash (diag. 68).
On models OHV
3/16"
ALLEN WRENCH
7/16"
CROWFOOT WRENCH
OHH / OVRM |
67 |
LOCKING / ADJUSTING NUT
CROWN DOWN
"O" RING OR GASKET
FEELER
GAUGE
VALVE STEM |
ROCKER ARM |
PUSH ROD |
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GUIDE |
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STUD |
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TABS UP |
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OVM / OHM / OVXL |
68 |
7/16"
SOCKET WRENCH
1/2"
CROWFOOT
WRENCH
OHV |
69 |
80
On models OHV 135 - 175 hold a 1/2" wrench on the rocker arm bearing while tightening the 5/32" Allen head set screw to 75 in. lbs. (8.5 Nm) of torque. Rotate the crankshaft at least one full turn to check push rod movement and valve lash (diag. 70).
Current production models OHV135 - 175 use a 1/2" wrench to tighten the rocker arm bearing to the correct valve lash. Once adjusted use a 1/2" socket and torque the jam nut to 130 inch pound (14.7 Nm). Rotate the crankshaft one full turn to check push rod movement and correct valve lash (diag. 71).
15.Install the rocker arm cover using a new gasket or
16.Attach the backing plates or baffles. Attach the governor arm lever if removed.
17.Attach the alternator coil if applicable and route the wires away from the flywheel area.
18.Install the flywheel spacer if applicable, flywheel key, flywheel, starter cup (if applicable), bevelled washer (concave surface in), and flywheel nut. Use strap wrench part # 670305 to hold the flywheel and tighten the nut to the specified torque.
19.Install the ignition module using a part # 670297 .0125" (.3175 mm) air gap tool between the flywheel magnets and the laminations of the module (diag. 72). Tighten the mounting screws, remove the tool, and check for contact while rotating the flywheel. None should be found. Attach the ignition ground lead to the module terminal.
20.Install the blower housing on all engines with the speed control mounted on the blower housing or engine block, and attach the ignition groundout lead at the control if applicable.
21.Install the intake pipe, speed control, carburetor, and air cleaner assembly while hooking the throttle and governor linkage. Install the blower housing on all engines with intake pipe mounted speed control brackets. Check the governor and speed control hook- up and adjustment - see Chapter 4 under "Service".
5/32"
ALLEN
WRENCH
1/2"
WRENCH
OHV135 - 17570
1/2"
TORQUE WRENCH
1/2"
WRENCH
71
.0125" (.3175 mm)
AIR GAP
72
81
22.Attach the fuel tank (if applicable) using bolts or wedging the tank in the blower housing slots provided. Attach the fuel line and secure with clamps.
23.Slide the fuel line on the carburetor fitting and secure with a clamp. Slide the breather tube on the carburetor or air cleaner fitting if applicable.
NOTE: If the tank is supplied by the O.E.M. replace the fuel filter. Tecumseh's tanks have a fuel filter in the tank and service is not necessary.
24.Fill the engine with oil to the full mark on the dipstick. Add fresh fuel to the fuel tank and secure the cap.
25.Install the spark plug and high tension lead. Mount the engine to the equipment and connect wiring and control cables. OVRM rotary mower engines require the blade to be secured to the blade hub adapter and crankshaft before attempting to start the engine.
26.Start the engine and allow it to run approximately five minutes to reach operating temperature. Optimize the carburetor if adjustable, verify top no load and idle RPM settings.
REMOVE |
BOLTS |
SLIDE TANK |
73 |
82
CHAPTER 10
ENGINE SPECIFICATIONS AND
SEARS CRAFTSMAN
The engine specifications listed on the following pages include tolerances that are considered acceptable to achieve normal engine operation. Observed values inside the listed tolerance range are satisfactory and require no adjustments.
OVERHEAD VALVE SEARS CRAFTSMAN CROSS REFERENCE
Craftsman |
Tecumseh |
Craftsman |
Tecumseh |
Craftsman |
Tecumseh |
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143.366012 |
143.406152 |
143.971200 |
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143.366072 |
143.406162 |
143.971201 |
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143.366202 |
143.414432 |
143.971300 |
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143.366212 |
143.416012 |
143.975003 |
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143.366232 |
143.416042 |
143.975005 |
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143.376012 |
143.416082 |
143.975009 |
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143.376032 |
143.426092 |
143.975501 |
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143.376072 |
143.426112 |
143.975503 |
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143.376082 |
143.426122 |
143.976001 |
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143.384132 |
143.426142 |
143.981200 |
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143.384142 |
143.426152 |
143.981201 |
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143.384152 |
143.426172 |
143.985001 |
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143.384162 |
143.436032 |
143.985005 |
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143.384182 |
143.436042 |
143.985501 |
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143.384192 |
143.436092 |
143.985503 |
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143.386012 |
143.436102 |
143.985505 |
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143.386032 |
143.436132 |
143.986001 |
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143.386092 |
143.436152 |
143.986003 |
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143.386102 |
143.796112 |
143.986702 |
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143.386152 |
143.806062 |
143.986704 |
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143.386162 |
143.816042 |
143.986714 |
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143.394092 |
143.836052 |
143.986716 |
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143.394102 |
143.941200 |
143.986718 |
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143.394112 |
143.941201 |
143.991200 |
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143.394192 |
143.951600 |
143.991201 |
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143.394202 |
143.951602 |
143.991203 |
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143.394212 |
143.951602 |
143.991300 |
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143.396012 |
143.955003 |
143.995007 |
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143.396032 |
143.955007 |
143.996001 |
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143.396062 |
143.961201 |
143.996005 |
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143.396072 |
143.965007 |
143.996007 |
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143.396092 |
143.965009 |
143.996009 |
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143.396112 |
143.965011 |
143.996501 |
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143.396132 |
143.965013 |
143.996503 |
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143.404112 |
143.965015 |
143.996505 |
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143.406012 |
143.965017 |
143.996507 |
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143.406052 |
143.965019 |
143.996702 |
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143.406062 |
143.965021 |
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143.406072 |
143.965023 |
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143.406132 |
143.965501 |
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143.406142 |
143.965503 |
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83
ENGINE SPECIFICATIONS
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OVRM40 |
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OVRM120 |
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OHH50 |
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Specifications |
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OVRM105 |
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OHSK50 |
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Standard |
Metric |
Standard |
Metric |
Standard |
Metric |
Standard |
Metric |
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English |
mm |
English |
mm |
English |
mm |
English |
mm |
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Displacement (in2) (cc) |
9.06 |
148.50 |
10.49 |
171.93 |
11.9 |
195.04 |
10.49 |
171.93 |
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Note (A) |
Note (A) |
Note (A) |
Note (A) |
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Stroke |
1.844 |
46.838 |
1.938 |
49.225 |
1.938 |
49.225 |
1.938 |
49.225 |
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Bore |
2.500 |
63.500 |
2.625 |
66.675 |
2.795 |
70.993 |
2.625 |
66.675 |
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2.501 |
63.525 |
2.626 |
66.700 |
2.796 |
71.018 |
2.626 |
66.700 |
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Note (B) |
Note (B) |
Note (B) |
Note (B) |
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Ignition Module Air Gap |
.0125 |
.3175 |
.0125 |
.3175 |
.0125 |
.3175 |
.0125 |
.3175 |
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Spark Plug Gap |
.030 |
.762 |
.030 |
.762 |
.030 |
.762 |
.030 |
.762 |
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Valve Clearance In./Ex. |
.004 |
.1016 |
.004 |
.1016 |
.004 |
.1016 |
.004 |
.1016 |
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.004 |
.1016 |
.004 |
.1016 |
.004 |
.1016 |
.004 |
.1016 |
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Valve Seat Angle |
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460 |
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460 |
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460 |
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460 |
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Valve Seat Width |
.035 |
.889 |
.035 |
.889 |
.035 |
.889 |
.035 |
.889 |
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.045 |
1.143 |
.045 |
1.143 |
.045 |
1.143 |
.045 |
1.143 |
||||||
Valve Guide Oversize |
INT. |
EX. |
INT. |
EX. |
INT. |
EX. |
INT. |
EX. |
INT. |
EX. |
INT. |
EX. |
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Dimension |
.2807 |
.2787 |
7.130 |
7.079 |
.2807 |
..2787 |
7.130 |
.7.079 |
.2807 |
..2787 |
7.130 |
.7.079 |
.2807 |
7.135 |
|
.2817 |
.2797 |
7.155 |
7.104 |
.2817 |
.2797 |
7.155 |
7.104 |
.2817 |
.2797 |
7.155 |
7.104 |
.2817 |
7.155 |
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Crankshaft End Play |
.006 |
.1524 |
.006 |
.1524 |
.006 |
.1524 |
.006 |
.1524 |
||||||
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.027 |
.6858 |
.027 |
.6858 |
.027 |
.6858 |
.027 |
.6858 |
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Note (C) |
Note (C) |
Note (C) |
Note (C) |
Note (C) |
Note (C) |
Note (C) |
Note (C) |
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Crankpin Journal Dia. |
.8610 |
31.869 |
.9995 |
25.362 |
.9995 |
25.362 |
.9995 |
25.362 |
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.8615 |
21.882 |
1.000 |
25.400 |
1.000 |
25.400 |
1.000 |
25.400 |
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Crankshaft Dia. Flywheel |
.9985 |
25.362 |
.9985 |
25.362 |
.9985 |
25.362 |
.9985 |
25.362 |
||||||
End Main Brg. |
.9990 |
25.375 |
.9990 |
25.375 |
.9990 |
25.375 |
.9990 |
25.375 |
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Crankshaft Dia. |
.9985 |
25.362 |
1.0005 |
25.413 |
1.0005 |
25.413 |
.9985 |
25.362 |
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P.T.O. Main Brg. |
.9990 |
25.375 |
1.0010 |
25.425 |
1.0010 |
25.425 |
.9990 |
25.375 |
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Conn. Rod Dia. Crank Brg. |
1.0005 |
25.413 |
1.0005 |
25.413 |
1.0005 |
25.413 |
1.0005 |
25.413 |
||||||
|
1.0010 |
25.425 |
1.0010 |
25.425 |
1.0010 |
25.425 |
1.0010 |
25.425 |
||||||
Camshaft Bearing Diameter |
.4975 |
12.637 |
.4975 |
12.637 |
.4975 |
12.637 |
.4970 |
12.624 |
||||||
|
.4980 |
12.649 |
.4980 |
12.649 |
.4980 |
12.649 |
.4975 |
12.637 |
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Piston Dia. Bottom of Skirt |
2.4950 |
63.373 |
2.6204 |
66.558 |
2.6204 |
66.558 |
2.6204 |
66.558 |
||||||
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2.4520 |
63.378 |
2.6220 |
66.599 |
2.6220 |
66.599 |
2.6220 |
66.599 |
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Ring Groove Side Clearance |
.0020 |
.051 |
.0020 |
.051 |
.0020 |
.051 |
.0020 |
.051 |
||||||
1st & 2nd Comp. |
.0050 |
.127 |
.0050 |
.127 |
.0050 |
.127 |
.0050 |
.127 |
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Ring Groove Side Clearance |
.0050 |
.013 |
.0050 |
.013 |
.0050 |
.013 |
.0050 |
.013 |
||||||
Bottom Oil |
.0035 |
.089 |
.0035 |
.089 |
.0035 |
.089 |
.0035 |
.089 |
||||||
Piston Skirt to Cylinder |
.0040 |
.102 |
.0030 |
.076 |
.0030 |
.076 |
.0030 |
.076 |
||||||
Clearance |
.0058 |
.147 |
.0056 |
.142 |
.0056 |
.142 |
.0056 |
.142 |
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Ring End Gap |
.010 |
.254 |
.010 |
.254 |
.010 |
.254 |
.007 |
.178 |
||||||
|
.020 |
.508 |
.020 |
.508 |
.020 |
.508 |
.017 |
.432 |
||||||
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Cylinder Main Bearing |
1.0005 |
25.413 |
1.0005 |
25.413 |
1.0005 |
25.413 |
1.0005 |
25.413 |
||||||
Diameter |
1.0010 |
25.425 |
1.0010 |
25.425 |
1.0010 |
25.425 |
1.0010 |
25.425 |
||||||
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Cylinder Cover / Flange |
1.0050 |
25.413 |
1.0050 |
25.413 |
1.0050 |
25.413 |
1.0050 |
25.413 |
||||||
Main Brg. Diameter |
1.0010 |
25.425 |
1.0010 |
25.425 |
1.0010 |
25.425 |
1.0010 |
25.425 |
||||||
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Note A: OVRM60, 21000 spec. numbers with a "B" suffix and all OVRM 65, 22000 spec. numbers have a displacement of 11.9 (195.04).
Note B: All OVRM 60, 21000 spec. numbers with a "B" suffix and all OVRM 65, 22000 spec. numbers have a 2.795"/2.796 (70.993/71.018) Bore.
Note C: All engines equipped with a ball bearing will have "0" End Play.
84
ENGINE SPECIFICATIONS (Continued)
|
OHH and |
OHSK80 - 110 |
OHM, OHSK, OVM, |
OHV13.5 - 17 |
||||
|
OHSK55 - 70 |
|
|
OVXL120,130 |
|
|
||
Specifications |
|
|
Note (D) |
& |
|
|
||
|
Standard |
Metric |
Standard |
Metric |
Standard |
Metric |
Standard |
Metric |
|
English |
mm |
English |
mm |
English |
mm |
English |
mm |
Displacement (in2) (cc) |
11.9 |
195.04 |
19.43 |
318.46 |
21.82 |
357.63 |
29.9 |
490.06 |
|
|
|
|
|
|
|
|
|
Stroke |
1.938 |
49.225 |
2.532 |
70.993 |
2.532 |
70.993 |
3.00 |
76.6 |
Bore |
2.795 |
70.993 |
3.125 |
79.375 |
3.312 |
84.125 |
3.562 |
90.475 |
|
2.796 |
71.018 |
3.126 |
79.400 |
3.313 |
84.150 |
3.563 |
90.500 |
|
|
|
|
|
|
|
|
|
Ignition Module Air Gap |
.0125 |
.3175 |
.0125 |
.3175 |
.0125 |
.3175 |
.0125 |
.3175 |
|
|
|
|
|
|
|
|
|
Spark Plug Gap |
.030 |
.762 |
.030 |
.762 |
.030 |
.762 |
.030 |
.762 |
|
|
|
|
|
|
|
|
|
Valve Clearance In./Ex. |
.004 |
.1016 |
.004 |
.1016 |
.004 |
.1016 |
.004 |
.1016 |
|
.004 |
.1016 |
.004 |
.1016 |
.004 |
.1016 |
.004 |
.1016 |
|
|
|
|
|
|
|
|
|
Valve Seat Angle |
460 |
460 |
460 |
460 |
||||
Valve Seat Width |
.035 |
.889 |
.035 |
.889 |
.035 |
.889 |
.042 |
1.0671 |
|
.045 |
1.143 |
.045 |
1.143 |
.045 |
1.143 |
.052 |
1.321 |
|
|
|
|
|
|
|
|
|
Valve Guide Oversize |
.2807 |
7.130 |
.3432 |
8.717 |
.3432 |
8.717 |
.3432 |
8.717 |
Dimension |
.2817 |
7.155 |
.3442 |
8.743 |
.3442 |
8.743 |
.3442 |
8.743 |
|
|
|
|
|
|
|
|
|
Crankshaft End Play |
.006 |
.1524 |
.002 |
.051 |
.002 |
.051 |
.0025 |
.064 |
|
.027 |
.6858 |
.042 |
.067 |
.042 |
.067 |
.0335 |
.851 |
|
Note (C) |
Note (C) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Crankpin Journal Dia. |
.9995 |
25.362 |
1.3740 |
34.900 |
1.3740 |
34.900 |
1.6223 |
41.206 |
|
1.000 |
25.400 |
1.3745 |
34.912 |
1.3745 |
34.912 |
1.6228 |
41.219 |
Crankshaft Dia. Flywheel |
.9985 |
25.362 |
1.3745 |
34.912 |
1.3745 |
34.912 |
1.6245 |
41.262 |
End Main Brg. |
.9990 |
25.375 |
1.3750 |
34.925 |
1.3750 |
34.925 |
1.6250 |
41.275 |
|
|
|
|
|
|
|
|
|
Crankshaft Dia. |
.9985 |
25.362 |
1.3745 |
34.912 |
1.3745 |
34.912 |
1.6245 |
41.206 |
P.T.O. Main Brg. |
.9990 |
25.375 |
1.3750 |
34.925 |
1.3750 |
34.925 |
1.6250 |
41.275 |
|
|
|
|
|
|
|
|
|
Conn. Rod Dia. Crank Brg. |
1.0005 |
25.413 |
1.3775 |
34.988 |
1.3775 |
34.988 |
1.6234 |
41.234 |
|
1.0010 |
25.425 |
1.3780 |
35.001 |
1.3780 |
35.001 |
1.6240 |
41.250 |
|
|
|
|
|
|
|
|
|
Camshaft Bearing Diameter |
.4970 |
12.624 |
.6230 |
15.824 |
.6230 |
15.824 |
.6235 |
15.837 |
|
.4975 |
12.637 |
.6235 |
15.837 |
.6235 |
15.837 |
.6240 |
15.850 |
Piston Dia. Bottom of Skirt |
2.7904 |
70.876 |
3.1195 |
79.235 |
3.3095 |
84.061 |
3.5595 |
90.411 |
|
2.7920 |
70.917 |
3.1205 |
79.261 |
3.3105 |
84.087 |
3.5605 |
90.437 |
|
|
|
|
|
|
|
|
|
Ring Groove Side Clearance |
.0020 |
.051 |
.0020 |
.051 |
.0020 |
.051 |
.0020 |
.051 |
1st & 2nd Comp. |
.0050 |
.127 |
.0040 |
.127 |
.0040 |
.127 |
.0040 |
.127 |
|
|
|
|
|
|
|
|
|
Ring Groove Side Clearance |
.0050 |
.013 |
.0010 |
.0254 |
.0010 |
.0254 |
.0009 |
.0229 |
Bottom Oil |
.0035 |
.089 |
.0030 |
.076 |
.0030 |
.076 |
.0029 |
.074 |
|
|
|
|
|
|
|
|
|
Piston Skirt to Cylinder |
.0030 |
.076 |
.0015 |
.038 |
.0015 |
.038 |
.0015 |
.038 |
Clearance |
.0056 |
.142 |
.0035 |
.089 |
.0035 |
.089 |
.0030 |
.089 |
|
|
|
|
|
|
|
|
|
Ring End Gap |
.007 |
.178 |
.010 |
.254 |
.010 |
.254 |
.012 |
.305 |
|
.017 |
.432 |
.020 |
.508 |
.020 |
.508 |
.022 |
.559 |
|
|
|
|
|
|
|
|
|
Cylinder Main Bearing |
1.0005 |
25.413 |
1.3765 |
34.963 |
1.3765 |
34.963 |
1.6265 |
41.313 |
Diameter |
1.0010 |
25.425 |
1.3770 |
34.976 |
1.3770 |
34.976 |
1.6270 |
41.326 |
|
|
|
|
|
|
|
|
|
Cylinder Cover / Flange |
1.0050 |
25.413 |
1.3765 |
34.963 |
1.3765 |
34.963 |
1.6265 |
41.313 |
Main Brg. Diameter |
1.0010 |
25.425 |
1.3770 |
34.976 |
1.3770 |
34.976 |
1.6270 |
41.326 |
|
|
|
|
|
|
|
|
|
Note A: OVRM60, 21000 spec. numbers with a "B" suffix and all OVRM 65, 22000 spec. numbers have a displacement of 11.9 (195.04).
Note B: All OVRM 60, 21000 spec. numbers with a "B" suffix and all OVRM 65, 22000 spec. numbers have a 2.795"/2.796 (70.993/71.018) Bore.
Note C: All engines equipped with a ball bearing will have "0" End Play.
Note D: For OHSK110 models with specification number starting with 223000 have a displacement of 21.82 ( 357.63 cc).
85
OVERHEAD VALVE TORQUE SPECIFICATIONS
The torque specifications listed in this chart are to be used for replacing components after disassembly, not for checking an existing engine bolt torque. Checking a torque value on a new or used engine may be lower due to torque relaxation that occurs on all engines from thermal expansion and contraction. However, sufficient clamping force exists and a
Specifications below ten ft. lbs. torque are listed only as in. lb. measurements to encourage the use of an inch pound torque wrench for greater torque accuracy.
|
|
|
|
|
|
OVXL, |
|
OHV |
|
|
|
ft. |
|
|
OHM, |
OHV |
203 Series |
||
|
In. lbs. |
Nm |
OVRM |
||||||
|
lbs. |
OVM, & |
|||||||
|
|
|
|
206 Series |
|||||
|
|
|
|
|
|
OHSK |
|
204 Series |
|
|
|
|
|
|
|
|
|
||
|
|
|
|
|
|
|
|
|
|
Cylinder Head Bolts |
230 |
19 |
26 |
X |
X |
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Conn. Rod Bolts |
105 |
- |
12 |
X |
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Conn. Rod Bolts |
220 |
18.3 |
24.8 |
|
|
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Cyl. Cover or Flange |
115 |
9.5 |
13 |
X |
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Cyl. Cover or Flange |
125 |
10.5 |
14 |
|
|
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Flywheel Nut |
450 |
35 |
51 |
X |
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Flywheel Nut Cast Iron |
550 |
46 |
62 |
|
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Flywheel Nut |
700 |
58 |
79 |
|
|
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Spark Plug |
250 |
21 |
28 |
X |
X |
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Ign. Mounting (Direct to Cyl.) |
45 |
- |
5 |
X |
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Ign. Mounting (Direct to Stud) |
45 |
- |
5 |
|
|
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Ign. Mounting Stud to Cyl. |
40 |
- |
4.5 |
|
|
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Intake Pipe to Head |
115 |
- |
13 |
X |
X |
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Carburetor to Intake Pipe |
70 |
- |
8 |
X |
X |
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Fuel Shut Off Solenoid to |
17 |
- |
2 |
|
|
|
X |
X |
X |
Carb. |
|
|
|
||||||
|
|
|
|
|
|
|
|
|
|
Muffler Mtg. (Flanged) |
75 |
- |
8.5 |
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Muffler Mtg. (Rect.) |
65 |
- |
7.5 |
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Muffler Mtg. |
45 |
- |
5 |
X |
|
|
|
|
|
(Oval) |
|
|
|
|
|
||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Muffler Mtg. |
100 |
- |
11.5 |
|
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Muffler (Flanged) to Manifold |
200 |
16.5 |
22.5 |
|
|
X |
|
X |
|
(Flanged) |
|
|
|
|
|||||
|
|
|
|
|
|
|
|
|
|
Muffler Clamp to Manifold |
80 |
- |
9 |
|
|
|
|
|
X |
|
|
|
|
|
|
|
|
|
|
3 |
|
|
FLAT WASHER |
|
2 |
|
4 |
||
|
|
|
|
|
|
|
|||
1 |
5 |
5 |
1 |
4 |
2 |
BELLEVILLE WASHER |
3 |
6 |
|
||||
|
TORQUE SEQUENCE |
|
TORQUE SEQUENCE |
|
|
(CROWN TOWARD BOLT HEAD) |
|
||
|
OVRM / OHH, OHSK |
OHV 11 - 17, OHM, OVM, OHSK110 - 120 |
||
|
|
|||
86
OVERHEAD VALVE TORQUE SPECIFICATIONS
The torque specifications listed in this chart are to be used for replacing components after disassembly, not for checking an existing engine bolt torque. Checking a torque value on a new or used engine may be lower due to torque relaxation that occurs on all engines from thermal expansion and contraction. However, sufficient clamping force exists and a
Specifications below ten ft. lbs. torque are listed only as in. lb. measurements to encourage the use of an inch pound torque wrench for greater torque accuracy.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
OVXL, |
OHSK & |
OHV |
203 Series |
|
In. |
|
|
|
OHM, |
OHV |
|||
|
lbs. |
ft. lbs. |
N/M |
OVRM |
OVM |
206 Series |
204 Series |
||
Manifold Mtg. (Shoulder Bolt) |
160 |
13.5 |
18 |
|
|
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Recoil Starter |
25 |
- |
3 |
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Recoil Starter |
50 |
- |
5.5 |
|
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
|
|
Recoil Starter |
40 |
- |
4.5 |
|
|
|
|
|
X |
|
|
|
|
|
|
|
|
|
|
Recoil Starter |
80 |
|
9 |
|
|
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
Electric Starter to Cylinder |
100 |
- |
11 |
X |
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
|
|
Electric Starter to Cylinder |
150 |
12.5 |
17 |
|
|
|
|
X |
X |
|
|
|
|
|
|
|
|
|
|
Rocker Arm Hex Jam Nut |
18 |
- |
2 |
|
|
X |
X 1 |
|
|
|
|
|
|
|
|
|
|
|
|
Rocker Arm Lock Allen |
75 |
- |
8.5 |
|
|
|
|
|
X |
Screw |
|
|
|
|
|
||||
|
|
|
|
|
|
|
|
|
|
Rocker Adjusting Jam Nut |
130 |
10.8 |
14.7 |
|
|
|
|
|
X 1 |
|
|
|
|
|
|
|
|
|
|
Rocker Arm Stud Lock Nut |
120 |
10 |
13.5 |
X |
X |
X |
X 1 |
X 1 |
|
|
|
|
|
|
|
|
|
|
|
Rocker Arm Studs |
190 |
15.8 |
21.5 |
|
|
X |
X |
|
X |
|
|
|
|
|
|
|
|
|
|
Rocker Box Cover |
40 |
- |
4.5 |
X |
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Rocker Box Cover |
18 |
- |
2 |
|
|
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
Rocker Box Cover |
55 |
- |
6 |
|
|
|
X |
X |
X |
(4 screws) |
|
|
|
||||||
|
|
|
|
|
|
|
|
|
|
Alt. Coil Assy. to Cylinder |
25 |
- |
3 |
|
|
|
|
|
X |
|
|
|
|
|
|
|
|
|
|
Alt. Coil Assy. to Cylinder |
65 |
- |
7 |
|
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Alt. Coil Assy. to Cylinder |
90 |
- |
10 |
|
|
X |
X |
X |
|
|
|
|
|
|
|
|
|
|
|
Alt. Coil Assy. to Lamination |
30 |
- |
3.5 |
X |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
NOTE 1: A jam nut is described as a nut which is placed above the rocker arm and bearing. A lock nut is positioned below the rocker arm and bearing.
87
CHAPTER 11. EDUCATIONAL MATERIALS
AND TOOLS
AVAILABLE TECHNICIAN'S HANDBOOKS 692508
Covers the diagnosis and repair of Tecumseh
692509
Covers the diagnosis and repair of the Tecumseh
691462A
Covers the diagnosis and repair of Tecumseh
691218
Covers the diagnosis and repair of Peerless® power train components.
694782
Contains technical information for the repair of the TC series,
694988
Contains diagnosis and technical information for the repair of TVS840, HSK/HXL845/850,
695244A
Covers the diagnosis and repair of the OVRM/OVM/ OHM/OHV
695578
Covers the diagnosis and repair of the Vector Series,
AVAILABLE FOREIGN TECHNICIAN'S
HANDBOOKS
694732 Spanish
This manual covers the following models:
VH80, VH100, HH80, HH100, HH120,
Covers the diagnosis and repair of the Tecumseh
695657 German
Covers the diagnosis and repair of the Tecumseh
695562 French
Covers the diagnosis and repair of the Tecumseh
VIDEO PROGRAMS
695015
Carburetor Troubleshooting. Covers identification of carburetors used on Tecumseh engines and how to troubleshoot and repair them. VHS only.
695059
Understanding Tecumseh Ignition Systems. A basic program designed to give the small engine technician first hand knowledge of Tecumseh ignition systems so the technician can understand the system and perform repairs to it. VHS only.
695148
Teardown and reassembly of the 900 series transaxles. This video will show a complete
88
695185
Electrical Troubleshooting. This video training program will assist the small engine technician in the proper procedures for troubleshooting electrical systems on outdoor power equipment.
695285
An
SPECIAL BOOKLETS
INSTRUCTIONAL GUIDE 692738
Assists in the use and understanding of the Tecumseh Master Parts Manual. Illustrates time saving features incorporated into the manual. Explains new carburetor parts breakdown format.
695590
This booklet is designed as a tool for the average technician to correctly assess the cause of failure.
CARBURETOR TROUBLESHOOTING BOOKLET 695907
This booklet is designed as a quick reference to carburetion problems and related repair procedures.
IGNITION SYSTEMS TROUBLESHOOTING BOOKLET
694903
This booklet contains information on the identification, possible problems and related repair procedures of Tecumseh Ignition Systems.
SPECIAL TOOLS BOOKLET 694862
This booklet depicts all specialty tools offered by Tecumseh which can be used on 2 and 4 cycle engines and Peerless units.
QUICK REFERENCE CHART BOOKLET 695933
This booklet contains the quick reference information found on Tecumseh wall charts.
This booklet is designed to be used as a work bench quick reference guide when servicing Tecumseh engines and motion drive systems.
TESTER BOOKLETS
694529
Test procedures for Tecumseh electrical components using
Test procedures for Tecumseh electrical components using
TOOL KIT 670195E
Kit contains tools for 2- and
Includes all items on this page but items may be purchased separately.
89
OIL SEAL DRIVER
No. 670195D Tool Kit. Contains special tools commonly used in servicing 2 and 4 cycle engines.
OIL SEAL PROTECTOR/INSTALLER
Consult the specification chart or measure the shaft diamteter to determine the correct tool.
Use with:
No. 670260.
No. 670263. 5/8" extended camshaft. No. 670264. 1/2" extended camshaft. No. 670277. 35/64"
No. 670292. 1" crankshaft bearing diameters assy. for recessed, raised, or flush seal position.
No. 670293. 7/8" crankshaft bearing diameters assy.for recessed or flush seal position.
No. 670308. Adapter for raised or flush seal position, used with 670309.
No. 670309.
No. 670310.
No. 670330.
No. 670335.
No. 670337. 1" to be used with 670265 and 670266 recessed and raised.
FLYWHEEL
†No. 670103 -
OIL SEAL REMOVER
Consult the specification chart or measure the shaft diamteter to determine the correct tool.
Use with:
No. 670287. 7/8" crankshaft bearing diameters. No. 670288. 3/4" crankshaft bearing diameters. No. 670289. 13/16" crankshaft bearing diameters. No. 670290. 1" crankshaft bearing diameters. No.
VIBRATION TACHOMETER
No. 670156 Vibration tachometer.
TAPER GAP GAUGE
No. 670256 Taper Gap Gauge
VALVE LAPPING TOOL
No. 670154A Valve lapping tool.
90
BUSHING TOOL KIT
OVRM AND
A.
B.
C.
D.
No. 670326
Rebushing tool kit for use on OHM, OHSK110, 120, OVM,
A.None
B.None
C.No. 670311 - Bushing Driver/Installer. No. 670317 - Bushing Driver/Installer.
No. 670298 Alignment Tool.
1/32" (.794 mm)
OVERSIZE VALVE GUIDE REAMER
No. 670283. Used on OHH on Intake and Exhaust, and
No. 670328. Used on
(7.079 - 7.104 mm).
No. 670284. Used on OVXL/OVM/OHM120, OVXL125 and
TORX DRIVERS |
|
Torx 8 |
670334 |
Torx 10 |
670333 |
Torx 15 |
670323 |
Torx 20 |
670324 |
Torx 25 |
670319 |
Torx 30 |
670320 |
RING EXPANDER
No. 670117
91