CHAPTER 1 GENERAL INFORMATION ....................... 1
ENGINE IDENTIFICATION ............................................. 1
INTERPRETATION OF MODEL NUMBER ..................... 1
SHORT BLOCKS............................................................. 2
FUELS ............................................................................. 2
ENGINE OIL .................................................................... 2
CAPACITIES.................................................................... 2
OIL CHANGE INTERVALS .............................................. 3
OIL CHECK...................................................................... 3
OIL CHANGE PROCEDURE .......................................... 3
TUNE-UP PROCEDURE ................................................. 3
STORAGE ....................................................................... 4
DRAINING THE FUEL SYSTEM ..................................... 4
OIL CYLINDER BORE .................................................... 4
CHAPTER 2 AIR CLEANERS ....................................... 5
GENERAL INFORMATION ............................................. 5
OPERATION .................................................................... 5
COMPONENTS ............................................................... 5
TROUBLESHOOTING OR TESTING ............................. 6
SERVICE ......................................................................... 6
DISASSEMBLY PROCEDURE ....................................... 6
POLYURETHANE-TYPE FILTER ELEMENT OR PRE-CLEANER..................................................... 7
PAPER -TYPE FILTER ELEMENT ................................. 7
FLOCKED SCREEN........................................................ 7
CHAPTER 3 CARBURETORS AND FUEL SYSTEMS . 8
GENERAL INFORMATION ............................................. 8
OPERATION .................................................................... 8
FUEL PRIMERS .............................................................. 9
IMPULSE FUEL PUMPS ................................................. 9
FLOAT STYLE CARBURETORS .................................... 9
CARBURETOR VISUAL IDENTIFICATION .................... 10
SERIES I CARBURETORS ............................................. 10
SERIES III & SERIES IV CARBURETORS .................... 10
SERIES VI CARBURETORS .......................................... 10
SERIES VII ...................................................................... 10
SERIES VIII ..................................................................... 11
SERIES IX ....................................................................... 11
WALBRO MODEL LMK ................................................... 11
TESTING ......................................................................... 12
SERVICE ......................................................................... 12
CARBURETOR PRE-SETS AND ADJUSTMENTS........ 12
PRE-SETS AND ADJUSTMENTS (TECUMSEH AND WALBRO CARBURETORS) ......... 13
FINAL ADJUSTMENTS ................................................... 13
TECUMSEH CARBURETORS ........................................ 13
WALBRO CARBURETOR ............................................... 13
CARBURETOR DISASSEMBLY PROCEDURE ............. 14
IMPULSE FUEL PUMP ................................................... 15
FLOAT ADJUSTING PROCEDURE................................ 16
INSPECTION ................................................................... 16
THROTTLE AND CHOKE ............................................... 16
IDLE AND HIGH SPEED MIXTURE ADJUSTING SCREW ........................................................................ 16
FUEL BOWL RETAINING NUT ....................................... 16
FUEL BOWL, FLOAT, NEEDLE AND SEAT ................... 17
ASSEMBLY PROCEDURE ............................................. 18
WELCH PLUGS............................................................... 18
THROTTLE SHAFT AND PLATE .................................... 18
CHOKE SHAFT AND PLATE .......................................... 19
FUEL INLET FITTING ..................................................... 19
HIGH AND LOW SPEED ADJUSTING SCREW, MAIN NOZZLE ............................................................. 19
INLET NEEDLE AND SEAT ............................................ 20
FLOAT INSTALLATION ................................................... 20
FUEL BOWL AND BOWL NUT ....................................... 21
IMPULSE FUEL PUMP ................................................... 21
PRIMER BULB ................................................................ 21
FINAL CHECKS............................................................... 21
CHAPTER 4 GOVERNORS AND LINKAGE ................. 22
GENERAL INFORMATION ............................................. 22
OPERATION .................................................................... 22
TROUBLESHOOTING .................................................... 22
ENGINE OVERSPEEDING ............................................. 22
ENGINE SURGING ......................................................... 22
SERVICE ......................................................................... 23
GOVERNOR ADJUSTMENT .......................................... 23
GOVERNOR GEAR AND SHAFT SERVICE .................. 23
GOVERNOR GEAR OR SHAFT REPLACEMENT, UPSET STYLE GOVERNOR SHAFT .......................... 23
GOVERNOR SHAFT REPLACEMENT, RETAINING RING STYLE ................................................................ 24
SPEED CONTROLS AND LINKAGE .............................. 25
CONVERSION TO REMOTE CONTROL ....................... 27
OVM, OVXL, OHV VERTICAL SPEED CONTROL ........ 28
OHV 11-17 HORIZONTAL SPEED CONTROL............... 28
CHAPTER 5 RECOIL STARTERS ................................. 29
GENERAL INFORMATION ............................................. 29
OPERATION .................................................................... 29
COMPONENTS ............................................................... 29
SERVICE ......................................................................... 29
ROPE SERVICE .............................................................. 29
ROPE RETAINER REPLACEMENT ............................... 30
STYLIZED REWIND STARTER (OHH, OVRM, OHM, OHSK, OVM, OVXL, OHV 11-13), AND STAMPED STEEL STARTER ......................................................... 30
DISASSEMBLY PROCEDURE ....................................... 30
ASSEMBLY PROCEDURE ............................................. 31
STYLIZED REWIND STARTER WITH PLASTIC RETAINER .................................................................... 31
DISASSEMBLY PROCEDURE ....................................... 31
ASSEMBLY ...................................................................... 32
KEEPER SPRING STYLE STARTERS .......................... 32
DISASSEMBLY PROCEDURE ....................................... 32
ASSEMBLY PROCEDURE ............................................. 33
STYLIZED STARTER (OHV 13.5 -17) ............................ 34
ASSEMBLY ...................................................................... 34
CHAPTER 6 ELECTRICAL SYSTEMS .......................... 35
GENERAL INFORMATION ............................................. 35
OPERATION .................................................................... 35
STARTING CIRCUIT AND ELECTRIC STARTERS ....... 35
CHARGING CIRCUIT ...................................................... 35
CONVERTING ALTERNATING CURRENT TO DIRECT CURRENT ...................................................... 36
HALF WAVE RECTIFIER SINGLE DIODE ..................... 36
FULL WAVE RECTIFIER BRIDGE RECTIFIER ............. 36
COMPONENTS ............................................................... 36
BATTERY......................................................................... 36
WIRING............................................................................ 36
ELECTRICAL TERMS ..................................................... 37
BASIC CHECKS .............................................................. 37
TROUBLESHOOTING ELECTRICAL STARTER CIRCUIT FLOW CHART .............................................. 38
TROUBLESHOOTING ELECTRICAL CHARGING CIRCUIT FLOW CHART .............................................. 39
TESTING PROCEDURE ................................................. 40
STARTING CIRCUIT ....................................................... 40
CHARGING CIRCUIT ...................................................... 40
350 MILLIAMP CHARGING SYSTEM ............................ 40
18 WATT A.C. LIGHTING ALTERNATOR....................... 41
35 WATT A.C. .................................................................. 41
2.5 AMP D.C., 35 WATT LIGHTING ............................... 41
3 AMP DC ALTERNATOR SYSTEM - DIODE IN HARNESS SLEEVE ..................................................... 42
5 AMP D.C. ALTERNATOR SYSTEM REGULATOR-RECTIFIER UNDER BLOWER HOUSING ..................................................................... 43
3 AMP D.C. 5 AMP A.C. ALTERNATOR ......................... 43
MODELS OVM/OVXL/OHV12.5 ..................................... 44
MODELS OHV 13.5 - 17 (3/5 AMP SPLIT)..................... 44
MODELS OVM/OVXL/OHV12.5 (RED BETWEEN ENGINE AND DIODE) .................... 44
MODELS OHV 13.5 - 17 (RED BETWEEN ENGINE AND DIODE) .................... 45
7 AMP D.C. ALTERNATOR SYSTEM REGULATOR-RECTIFIER UNDER ENGINE HOUSING ..................................................................... 45
10 AMP A.C. ALTERNATOR ........................................... 46
16 AMP ALTERNATOR SYSTEM WITH EXTERNAL REGULATOR ................................................................ 46
VOLTAGE REGULATORS .............................................. 46
FUEL SHUT-DOWN SOLENOIDS .................................. 46
LOW OIL SHUTDOWN SWITCHES ............................... 47
LOW OIL PRESSURE SENSOR .................................... 47
LOW OIL SENSOR.......................................................... 47
ELECTRIC STARTER SERVICE .................................... 48
12 VOLT OR 120 VOLT ELECTRIC STARTERS ........... 48
INSPECTION AND REPAIR ............................................ 49
BRUSH CARD REPLACEMENT..................................... 49
CHAPTER 7 FLYWHEEL BRAKE SYSTEMS ............... 50
GENERAL INFORMATION ............................................. 50
OPERATION .................................................................... 50
COMPONENTS ............................................................... 51
SERVICE ......................................................................... 51
BRAKE BRACKET ASSEMBLY ...................................... 52
IGNITION GROUNDOUT TERMINAL............................. 52
STARTER INTERLOCK SWITCH ................................... 52
CONTROL CABLE .......................................................... 52
BRAKE BRACKET REPLACEMENT .............................. 52
CHAPTER 8 IGNITION ................................................... 53
GENERAL INFORMATION ............................................. 53
OPERATION .................................................................... 53
SOLID STATE IGNITION SYSTEM (CDI) ....................... 53
COMPONENTS ............................................................... 53
TESTING PROCEDURE ................................................. 54
FOUR CYCLE IGNITION TROUBLESHOOTING........... 55
SERVICE ......................................................................... 56
SPARK PLUG SERVICE ................................................. 56
CONDITIONS CAUSING FREQUENT SPARK PLUG FOULING ........................................................... 56
IGNITION TIMING CHECK ............................................. 57
SERVICE TIPS ................................................................ 57
CHAPTER 9 INTERNAL ENGINE AND CYLINDER ..... 58
GENERAL INFORMATION ............................................. 58
OPERATION .................................................................... 58
4-CYCLE ENGINE THEORY .......................................... 58
LUBRICATION SYSTEMS .............................................. 59
COUNTERBALANCE SYSTEMS ................................... 59
COMPONENTS ............................................................... 60
ENGINE OPERATION PROBLEMS ............................... 61
ENGINE OPERATION PROBLEMS ............................... 62
TESTING ......................................................................... 63
ENGINE KNOCKS ........................................................... 63
ENGINE OVERHEATS .................................................... 63
SURGES OR RUNS UNEVENLY ................................... 63
ENGINE MISFIRES ......................................................... 63
ENGINE VIBRATES EXCESSIVELY .............................. 64
BREATHER PASSING OIL ............................................. 64
EXCESSIVE OIL CONSUMPTION ................................. 64
LACKS POWER .............................................................. 65
SERVICE ......................................................................... 65
DISASSEMBLY PROCEDURE ....................................... 65
CYLINDERS .................................................................... 68
CYLINDER HEAD AND VALVE TRAIN SERVICE ......... 69
VALVES, SPRINGS, AND PUSH RODS ........................ 69
PISTONS, RINGS, AND CONNECTING RODS ............. 70
PISTON ........................................................................... 70
PISTON RINGS ............................................................... 70
PISTON RING ORIENTATION ....................................... 70
CONNECTING RODS ..................................................... 71
CRANKSHAFTS AND CAMSHAFTS .............................. 71
CAMSHAFTS................................................................... 71
VALVE SEATS ................................................................. 72
VALVE LIFTERS .............................................................. 73
VALVE GUIDES ............................................................... 73
VALVE GUIDE REMOVAL (OVM, OHM, OHSK110 & 120, OVXL ONLY) .................................................... 73
VALVE GUIDE INSTALLATION (OVM, OHM, OHSK110 & 120, OVXL ONLY) ................................... 73
CRANKCASE BREATHERS ........................................... 74
TOP MOUNTED BREATHER ......................................... 74
SIDE MOUNTED BREATHER ........................................ 74
CYLINDER COVER, OIL SEAL, AND BEARING SERVICE ...................................................................... 75
CYLINDER COVER ........................................................ 75
OIL SEAL SERVICE ........................................................ 75
CRANKSHAFT BEARING SERVICE .............................. 75
BALL BEARING SERVICE.............................................. 75
SERVICE BUSHING ....................................................... 76
BUSHING SIZE CHART.................................................. 76
ENGINE ASSEMBLY ...................................................... 76
CHAPTER 10 .................................................................. 83
ENGINE SPECIFICATIONS AND SEARS CRAFTSMAN CROSS-REFERENCE ......................... 83
OVERHEAD VALVE SEARS CRAFTSMAN CROSS REFERENCE ................................................. 83
ENGINE SPECIFICATIONS............................................ 85
OVERHEAD VALVE TORQUE SPECIFICATIONS ........ 86
OVERHEAD VALVE TORQUE SPECIFICATIONS ........ 87
CHAPTER 11 EDUCATIONAL MATERIALS AND TOOLS ............................................................... 88
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