Main Menu 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, OVRM40-675, OVRM120, OVXL/C120, OVXL120, OVXL125. 4-CYCLE OVERHEAD VALVE ENGINES 740043 ENGINE AND TRANSMISSION GROUP Engine & Transmission Sales Office European Sales Office Service Division & Group Offices 900 North Street Grafton, WI 53024 Phone: 414-377-2700 FAX: 414-377-4485 Tecumseh Europa S.p.A. Strada delle Cacce, 99 10135 Torino, Italy Tel.
Main Menu CONTENTS Page CHAPTER 1 GENERAL INFORMATION ....................... 1 ENGINE IDENTIFICATION ............................................. 1 INTERPRETATION OF MODEL NUMBER ..................... 1 SHORT BLOCKS ............................................................. 2 FUELS ............................................................................. 2 ENGINE OIL .................................................................... 2 CAPACITIES .................................................
Main Menu Page 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 ...............................
Main Menu 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.
Main Menu SHORT BLOCKS SBV OR SBH IDENTIFICATION NUMBER 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). SHORT BLOCK IDENTIFICATION TAG SBV- 564A SER 5107 THIS SYMBOL POINTS OUT IMPORTANT SAFETY INSTRUCTIONS WHICH IF NOT FOLLOWED COULD ENDANGER THE PERSONAL SAFETY OF YOURSELF AND OTHERS.
Main Menu Oil Change Intervals: Change the oil after the first two (2) hours of operation and every 25 hours thereafter (OHH & OHSK50-130, OHV13.5-17 every 50 hours), or more often if operated under dusty or dirty conditions. If the engine is run less than 25 hours per year, change the oil at least once per year. NOTE: The oil filter (if equipped) requires changing every 100 hours or more often if operated under dusty or dirty conditions.
Main Menu 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.
Main Menu 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 paper-type air filter system.
Main Menu 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 paper-type air filter should only be replaced.
Main Menu Polyurethane-Type Filter Element or pre-cleaner This type of air filter or pre-cleaner can be serviced when restricted with dust or dirt. Wash the filter or precleaner in a detergent and water solution until all the dirt is removed. Rinse in clear water to remove the detergent solution. Squeeze the filter or pre-cleaner (do not twist) to remove the excess water. Wrap the filter or pre-cleaner in a clean cloth and squeeze it (do not twist) until completely dry.
Main Menu 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.
Main Menu 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.
Main Menu 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).
Main Menu 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.
Main Menu TESTING 1. After repeated efforts to start the engine using the procedure listed in the operators 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.
Main Menu Pre-sets and Adjustments (Tecumseh and Walbro carburetors) Tecumseh Carburetors 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 pre-set figure in the chart shown. NOTE: SOME CARBURETORS HAVE FIXED IDLE AND MAIN JETS. IDENTIFY THE SERIES OF CARBURETOR USING THE VISUAL IDENTIFICATION IN THIS CHAPTER.
Main Menu 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.
Main Menu 8. Remove the primer bulb (if equipped) by grasping with a pliers and pulling and twisting out of the body. Remove the retainer by prying and lifting out with a screwdriver. Do not reuse old bulb or retainer (diag. 28). 9. Remove all welch plugs if cleaning the carburetor. Secure the carburetor in a vise equipped with protective jaws. Use a small chisel sharpened to a 1/8" (3.175 mm) wide wedge point.
Main Menu 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.
Main Menu 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.
Main Menu 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).
Main Menu Choke Shaft and Plate The choke plate is inserted into the air horn of the carburetor in such a position that the flat surface (if applicable) of the choke is down. Choke plates will operate in either direction. Make sure it is assembled properly for the engine. Test the operation of the choke and return spring function if equipped (diag. 46). CHOKE PLATE Always use a new screw(s) when reinstalling the choke shutter as the screws are treated with dry-type adhesive to secure them in place.
Main Menu 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 5/32" (3.
Main Menu 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. DETENT 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.
Main Menu 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.
Main Menu 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).
Main Menu 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.
Main Menu 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.
Main Menu NOTE: Early production OHH engines did not have governed idle, set only the idle crack screw and high speed governor stop.
Main Menu 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 SCREW LOCK NUT CONTROL KNOB GROUNDING TERMINAL WAVE WASHER ADDITION BOWDEN WIRE BRACKET 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.
Main Menu 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.
Main Menu 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.
Main Menu 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. STAPLE 2. Slide the rope retainer into the proper position and insert the staple using a pliers. 3.
Main Menu 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 spring hook into the deep notch in the pulley.
Main Menu 4. Use a small Phillips screwdriver or similar tool to pry the retainer legs apart and lift out the retaining wedge. RETAINING WEDGE (STEEL CLIP - NEW STYLE) 5. Pinch the legs of the retainer together and pull on the head of the retainer to remove it from the housing. STARTER HOUSING 6. Remove the pulley assembly from the recoil housing. 7. Repair or replace as necessary. Assembly STARTER PULLEY SPRING & COVER 1. If replacing the starter rope, see Step 8. 2.
Main Menu Assembly Procedure HOUSING 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. HANDLE SPRING & KEEPER ASSY. PULLEY BRAKE SPRING RETAINER DOG SPRNG RETAINER SCREW 2. Place the pulley assembly into the starter housing. "STAMPED STEEL" CENTER PIN 11 3.
Main Menu Stylized Starter (OHV 13.5 -17) 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. STARTER HOUSING REWIND SPRING 2. Untie the temporary knot and slowly allow the rope to fully retract into the starter housing and the recoil spring to fully unwind. PULLEY 3. Remove the nut (using a 10 mm socket) and washers from the center leg of the recoil housing.
Main Menu 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.
Main Menu CONVERTING ALTERNATING CURRENT TO DIRECT CURRENT CATHODE ANODE 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.
Main Menu WIRE GAUGE: The proper thickness of wire is necessary in all electrical circuits. Wire diameter is measured in increments of gauge numbers. As the gauge number of the wire increases, the wire diameter decreases in size (diag. 6). THE LARGER THE NUMBER THE SMALLER THE WIRE # 18 1. The starter circuit wiring must be rated at #6 or lower gauge number. 2. The charging circuit wiring must be rated at #16 or lower gauge number (20 amp system requires #14 or lower gauge number). #6 6 3.
Main Menu TROUBLESHOOTING ELECTRICAL STARTER CIRCUIT FLOW CHART NO YES Is there power at the power source? Repair or replace power source Starter turns at low rpms or stalls under load Intermittent starter operation Starter will not turn NO Is power supplied to the starter terminal? Check wiring, connections, safety switches, starter switch Check starter for binding brushes, worn brushes, dirty or oily commutator Internal engine failure or flywheel interference YES NO NO Isolate engine from
Main Menu TROUBLESHOOTING ELECTRICAL CHARGING CIRCUIT FLOW CHART 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 NO NO Is the voltage greater than or equal to the minimum value? Is AC voltage before diode or YES rectifier greater than the minimum value? Alt
Main Menu 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.
Main Menu 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). ENGINE With the engine running, minimum A.C.
Main Menu 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.
Main Menu 5 AMP D.C. ALTERNATOR SYSTEM REGULATOR-RECTIFIER UNDER BLOWER HOUSING 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 regulator-rectifier must be brought outside of the blower housing. Reinstall the blower housing. Disconnect the red D.C. output connector at the wiring harness and connect the probes from an A.C.
Main Menu 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) RED 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) DIODE YELLOW D.C. D.C. 2500 R.P.M. - 8.5 Volts A.C. 3000 R.P.M. - 11.0 Volts A.C. 3600 R.P.M.
Main Menu Models OHV 13.5 - 17 (Read between Engine and Diode) A.C. 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. RED If low or no voltage is experienced, replace the alternator. If the alternator puts out the minimum A.C. voltage, replace the diode. DIODE YELLOW 19 7 Amp D.C.
Main Menu 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). A.C. OUTPUT YELLOW A.C. With the engine running, minimum values should read: 22 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.
Main Menu 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.
Main Menu 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.
Main Menu 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.
Main Menu 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.
Main Menu 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.
Main Menu 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.
Main Menu 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.
Main Menu 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.
Main Menu FOUR CYCLE IGNITION TROUBLESHOOTING Engine runs erratically or shuts off, restarts Engine Will Not Start Check for spark Spark No Spark Replace spark plug Check for the correct spark plug Check flywheel and key for damage or sheared key Set proper air gap on ignition module Test ignition module for intermittent or weak spark Check electric starter and battery if applicable Isolate engine from equipment and repeat test Spark Equipment problem, check switches, wiring and equipment controls
Main Menu SERVICE To remove the ignition module or the flywheel from the engine, see Chapter 9 under "Disassembly". GAP GAUGE (670256) SPARK PLUG SERVICE Spark plugs should be removed, cleaned, and adjusted periodically. Check the air gap with a spark plug gap gauge and adjust accordingly. Set the spark plug gap at .030" (.762 mm) (diag. 5). Replace the plug if the points on the base of the plug are pitted or burned, or if the porcelain is cracked anywhere.
Main Menu IGNITION TIMING CHECK In order for an engine to run effectively and efficiently, the spark must ignite the compressed air-fuel mixture when the piston is in a specific position to deliver maximum power. This position is known as Before Top Dead Center (BTDC). If the mixture is ignited too soon, kickback can be experienced due to preignition. If the mixture is ignited too late, loss of power can be experienced due to retarded spark.
Main Menu 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.
Main Menu 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.
Main Menu 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.
Main Menu ENGINE OPERATION PROBLEMS ENGINE KNOCKS OVERHEATS SURGES OR RUNS UNEVENLY Associated equipment loose or improperly adjusted Excessive engine loading Fuel cap vent obstructed Check for excessive carbon in combustion chamber Low oil level or wrong viscosity oil Dirty carburetor or air filter Loose flywheel examine key, key way and proper flywheel nut torque Cooling air flow obstructed or clogged cooling fins Carburetor improperly adjusted Ignition timing or incorrect spark plug Carbure
Main Menu ENGINE OPERATION PROBLEMS ENGINE MISFIRES ENGINE VIBRATES EXCESSIVELY BREATHER PASSING OIL Carburetor improperly adjusted Bent crankshaft Oil level too high Wrong or fouled spark plug Attached equipment out of balance Excessive RPM or improper governor setting Valves sticking or not seating properly Loose mounting bolts Damaged gaskets, seals or "O" rings If applicable counter balance not properly aligned Breather damaged, dirty or improperly installed Ignition timing or incorrect
Main Menu 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 re-torque the bolts to the proper torque. 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.
Main Menu 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.
Main Menu 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.
Main Menu 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.
Main Menu 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.
Main Menu 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" (12.7-19.05 mm) from the top and the bottom .
Main Menu 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.
Main Menu PISTONS, RINGS, AND CONNECTING RODS INDICATES .010" (.254 mm) OVERSIZE PISTON 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.
Main Menu 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.
Main Menu 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). CAMSHAFT COMPRESSION RELEASE Some OHH engines use a composite camshaft.
Main Menu 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.
Main Menu CRANKCASE BREATHERS TUBE 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. CHECK VALVE ELEMENT 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.
Main Menu 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.
Main Menu 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 PART NUMBER FINISHED REAM BORE DIAMETER 30979 .............................................................. .8755 - .8760" (22.226 - 22.250 mm) 31461 .............................................................. 1.0000 - 1.0005" (25.
Main Menu 5. Assemble the compression release components to the camshaft on engine models OHH and OHSK50-70. Install spring end "A" through the release from the pin side, insert spring end "B" through the camshaft gear, and slide the release pin in the small hole near the center of the cam gear. Assemble the thrust washer on the camshaft next to the compression release. (diag.
Main Menu 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.
Main Menu Install the cylinder head using a new head gasket. On OHV 11-13 models, place the push rods in the block before installing the head and head gasket. Tighten the head bolts in the numbered sequence using 60 inch pound (6.8 Nm) increments to the specified torque. NOTE: Tecumseh strongly recommends you order a complete seal kit. Replace all "O" ring and gaskets in kit. DAMPENING COILS LOCATED CLOSER TOGETHER FREE LENGTH 1.980" (50.
Main Menu 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. 3/16" ALLEN WRENCH NOTE: TORQUE THE CYLINDER HEAD FOLLOWING THE SEQUENCE ON PAGE 69. 7/16" CROWFOOT WRENCH 13. On engine models OHH and OVRM, install the push rods on the lifters, and rocker arms and locking nuts on the rocker arm pivot screws.
Main Menu On models OHV 135 - 175 hold a 1/2" (12.7 mm) wrench on the rocker arm bearing while tightening the 5/32" Allen head set screw to 175 in. lbs. (8.5 Nm) of torque. Rotate the crankshaft at least one full turn to check push rod movement and valve lash. 15. Install the rocker arm cover using a new gasket or o-ring and tighten the screws (with new "O"rings on OVM, OHM, OVXL) to the specified torque. Connect the breather hose to the valve cover fitting on model OHH. 16.
Main Menu CHAPTER 10 ENGINE SPECIFICATIONS AND SEARS CRAFTSMAN CROSS-REFERENCE 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 143.366012 143.366072 143.366202 143.366212 143.366232 143.376012 143.376032 143.376072 143.376082 143.384132 143.384142 143.384152 143.
Main Menu ENGINE SPECIFICATIONS OVRM40 Specifications OVRM50-6.75 OVRM105 Standard Metric English mm 10.49 171.93 Note (A) Note (A) Standard English 9.06 Metric mm 148.50 Stroke 1.844 46.838 1.938 Bore 2.500 2.501 63.500 63.525 Displacement (in2) (cc) OVRM120 OHH50 OHSK50 Standard Metric English mm 10.49 171.93 Standard English 11.9 Note (A) Metric mm 195.04 Note (A) 49.225 1.938 49.225 1.938 49.225 2.625 2.626 Note (B) 66.675 66.700 Note (B) 2.795 2.796 Note (B) 70.993 71.
Main Menu ENGINE SPECIFICATIONS Specifications Displacement (in2) (cc) OHH and OHSK55 - 70 Standard Metric English mm 11.9 195.04 OHSK80 - 110 Note (D) Standard Metric English mm 19.43 318.46 (Continued) OHM, OHSK, OVM, OHV13.5 - 17 OVXL120,130 & OHV11-13 Standard Metric Standard Metric English mm English mm 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 2.796 70.993 71.018 3.125 3.126 79.375 79.400 3.312 3.313 84.125 84.150 3.562 3.563 90.
Main Menu 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 re-torque is not necessary. Specifications below ten ft. lbs. or ten Nm torque are listed only as in. lb.
Main Menu 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 re-torque is not necessary. Specifications below ten ft. lbs. or ten Nm torque are listed only as in. lb.
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Main Menu CHAPTER 11. EDUCATIONAL MATERIALS AND TOOLS AVAILABLE TECHNICIAN'S HANDBOOKS 692508 Covers the diagnosis and repair of Tecumseh 2-cycle engines. Except the TC Engine and TVS840. 692509 Covers the diagnosis and repair of the Tecumseh 4-cycle light/medium frame engines. 691462A Covers the diagnosis and repair of Tecumseh 4-cycle large frame engines. 691218 Covers the diagnosis and repair of Peerless® power train components.
Main Menu TOOLS TOOL KIT 670195E Kit contains tools for 2- and 4-cycle engines. Includes all items on this page but items may be purchased separately.
Main Menu 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. 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.
Main Menu BUSHING TOOL KIT OVRM AND OHV11-16.5 SPEED ADJUSTMENT TOOL B. A. C. D. Rebushing tool kit for use on OHM, OHSK110, 120, OVM, OHV11-13 AND OVXL. 1-3/8" main bearing. No. 670326 TORX DRIVERS A. None Torx 8 670334 B. None Torx 10 670333 C. No. 670311 - Bushing Driver/Installer. Torx 15 670323 No. 670317 - Bushing Driver/Installer. Torx 20 670324 Torx 25 670319 Torx 30 670320 No. 670298 Alignment Tool. 1/32" (.794 mm) OVERSIZE VALVE GUIDE REAMER No. 670283.
