4-CYCLE OVERHEAD VALVE ENGINES - Small Engine Discount

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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- GUIDES 20 minutes until the oil begins to smoke. Oil temperature must be 375 o - 400 o F (190 0 - HEAD 204 0 C). CAUTION : USE PROTECTION FOR EYES OIL AND HANDS, BE CAREFUL ! THE HOT OIL AND HEAD CAN EASILY CAUSE BURNS. HOT PLATE 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 HEAT UNTIL OIL BEGINS TO SMOKE 43 new guides in place. 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 15-20 minutes until the oil begins to smoke. Oil temperature must be 375 o - 400 o F (190 0 - 204 0 C). 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 re-cut both valve seats using a Neway cutter to align the new guides to the valve seats. Not For Resale www.SmallEngineDiscount.com 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. 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. COVER ELEMENT BAFFLE OIL RETURN GASKET BODY REED DRAIN HOLE PRESSURE OUT 46 FILTER BODY GASKET TUBE CHECK VALVE COVER 44 45 TUBE 47 2 1 4 5 BREATHER OUTLET TO CARB UMBRELLA 74 3 1 - Valve, Reed 2 - Plate, Limit 3 - Screw 4 - Baffle/Gasket 5 - Cover 48 Not For Resale www.SmallEngineDiscount.com 49
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Not For Resale www.SmallEngineDisco
Page 3 and 4:
Page TESTING PROCEDURE ............
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SHORT BLOCKS SBV OR SBH IDENTIFICAT
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STORAGE (IF THE ENGINE IS TO BE UNU
Page 9 and 10:
TROUBLESHOOTING OR TESTING If the e
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8 CHAPTER 3 CARBURETORS AND FUEL SY
Page 13 and 14:
CARBURETOR VISUAL IDENTIFICATION Se
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TESTING 12 1. After repeated effort
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If further adjustment is required,
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FLOAT ADJUSTING PROCEDURE All Tecum
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ASSEMBLY PROCEDURE Welch Plugs To i
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Inlet Needle and Seat Make sure the
Page 25 and 26: 22 CHAPTER 4 GOVERNORS AND LINKAGE
Page 27 and 28: Governor Shaft Replacement, Retaini
Page 29 and 30: NOTE: Early production OHH engines
Page 31 and 32: OVM, OVXL, OHV VERTICAL SPEED CONTR
Page 33 and 34: CAUTION: HANDLE MATCHES SAFELY TO A
Page 35 and 36: 32 4. Use a small Phillips screwdri
Page 37 and 38: Stylized Starter (OHV 13.5 -17) 34
Page 39 and 40: CONVERTING ALTERNATING CURRENT TO D
Page 41 and 42: TROUBLESHOOTING ELECTRICAL STARTER
Page 43 and 44: TESTING PROCEDURE STARTING CIRCUIT
Page 45 and 46: 3 AMP DC ALTERNATOR SYSTEM - DIODE
Page 47 and 48: CHECKING THE SYSTEM: To check the s
Page 49 and 50: 10 Amp A.C. Alternator CHECKING THE
Page 51 and 52: LOW OIL PRESSURE SENSOR Test the se
Page 53 and 54: CHAPTER 7 FLYWHEEL BRAKE SYSTEMS GE
Page 55 and 56: BRAKE BRACKET ASSEMBLY Late product
Page 57 and 58: The flywheel with magnets provide t
Page 59 and 60: SERVICE To remove the ignition modu
Page 61 and 62: CHAPTER 9 INTERNAL ENGINE AND CYLIN
Page 63 and 64: COMPONENTS The cylinder block house
Page 65 and 66: ENGINE OPERATION PROBLEMS ENGINE MI
Page 67 and 68: ENGINE VIBRATES EXCESSIVELY 64 1. R
Page 69 and 70: 10. Remove the flywheel key and alt
Page 71 and 72: CYLINDERS Visually check the cylind
Page 73 and 74: PISTONS, RINGS, AND CONNECTING RODS
Page 75: Mechanical Compression Release (MCR
Page 79 and 80: SERVICE BUSHING We are supplying th
Page 81 and 82: 8. Mount the cylinder cover or flan
Page 83 and 84: 13. On engine models OHH and OVRM,
Page 85 and 86: 22. Attach the fuel tank (if applic
Page 87 and 88: 84 ENGINE SPECIFICATIONS OVRM40 OVR
Page 89 and 90: OVERHEAD VALVE TORQUE SPECIFICATION
Page 91 and 92: CHAPTER 11. EDUCATIONAL MATERIALS A
Page 93 and 94: OIL SEAL DRIVER OIL SEAL REMOVER No
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4-CYCLE OVERHEAD VALVE ENGINES - Small Engine Discount

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