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Tecumseh 695244a Technician'S Handbook Download Page 75

72

SEAT CUTTER

SEAT

42

41

31

0

SEAT

40

15

0

60

0

BOTTOM

NARROWING

CUTTER

BOTTOM

NARROW

3/64" SEAT

TOP

NARROW

TOP NARROWING

CUTTER

46

0

31

0

46

0

BOTTOM

NARROWING

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 50-70 engines that

have been manufactured after DOM (date of

manufacture) 7048.  This change that took place in

February of 1997 and is basic on the OHH engines,

except those units that use extended camshafts which

will continue to use a cast iron camshaft.   A camshaft

kit replaces the old camshaft and includes

compression release components and two light tension

valve springs.  It is 

CRITICAL

 that the new valve

springs be installed or lobe damage will occur on the

camshaft.

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).

38

39

CAMSHAFT

COMPRESSION

RELEASE SPRING

COMPRESSION

RELEASE

A

B

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 # 100-1/4-1 for the .249" (6.325 mm) exhaust guide, and

Neway #100-1/4 for the .250" (6.35 mm) intake guide. Consult the cutter's complete procedure guide for

additional information.
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. Re-cut the seat to move the contact area higher or

lower if necessary and recheck the contact area.

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).

INSERT

SPRING

END "A"

THRUST

WASHER

EXHAUST

INTAKE

www.mymowerparts.com

For  Discount Tecumseh Engine Parts Call 606-678-9623 or 606-561-4983

Summary of Contents for 695244a

Page 1: ...cle Engine 4 Cycle Engine and Transmission manuals booklets and wall charts are available through Tecumseh For complete listing write or call CONTAINS SEARS CRAFTSMAN CROSS REFERENCE 4 CYCLE OVERHEAD VALVE ENGINES T E C H N I C I A N S H A N D B O O K TECUMSEH www mymowerparts com For Discount Tecumseh Engine Parts Call 606 678 9623 or 606 561 4983 ...

Page 2: ...STING 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 G...

Page 3: ...UBRICATION 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 ...

Page 4: ...tion The serial number or D O M indicates the production date of the engine Using model OHV16 204207A serial 5215C as an example interpretation is as follows OHV16 204207A is the model and specification number OHV Overhead Valve Vertical 16 Indicates 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 ...

Page 5: ... 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 TECUMSE...

Page 6: ...f poor engine performance The following is a minor tune up procedure When this procedure is completed the engine should operate 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 an...

Page 7: ...t 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 wh...

Page 8: ...ary 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 A polyurethane pre cleaner or a flocked screen may be used with the main filter Snow King engines do not use an air filter due t...

Page 9: ...r 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 A paper type filter cannot have an oil film presen...

Page 10: ...eaner housing and cover being careful not to allow dirt to fall into the carburetor or intake pipe Paper type filter element 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 th...

Page 11: ...ering the engine enters through openings around the shutter As the starting device is operated to start the engine downward piston travel creates a low air pressure area in the engine cylinder above the piston Higher pressure atmospheric air rushes into the engine to fill the created low pressure area Since the majority of the air passage is blocked by the choke shutter a relatively small quantity...

Page 12: ...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 carb...

Page 13: ...ottle 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 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...

Page 14: ... Dealer 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 16 Serie...

Page 15: ...l 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...

Page 16: ...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 ID...

Page 17: ...t 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 carbur...

Page 18: ...ough 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 28 30 31 29 WELCH PLUG TO BE REMOVED PIERCE PLUG WITH TIP DO NOT ALLOW CHISEL POINT TO STRIKE CARBURETOR BODY OR CHANNEL REDUCER ABOUT 1 8 3 175 mm WIDE BALL PLUG IDLE FUEL PASSAGE REDUCT...

Page 19: ...owl 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 ...

Page 20: ...tarvation 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 CHOKE SHAFT THROTTLE SHAFT CHOKE DUST SEAL CHOKE RETURN SPRING BOWL NUT BOWL NUT WASHER FLOAT BOWL O RING FLOAT FLOAT SHAFT SCREW FUEL FITTING INLET NEEDLE THROTTLE SHUTTER CHOKE SHUTTER WELCH PLUG TENSION SPRING IDLE MIXTUR...

Page 21: ...osening the screws and repositioning throttle plate Always use a new screw s when reinstalling the throttle shutter to prevent the screws from loosening and being drawn into the engine New Tecumseh screws are treated with dry type adhesive to secure them in place NOTE NEVER REUSE OLD SCREWS On Walbro LMK and Series 7 carburetors install the throttle return spring on the throttle shaft with the squ...

Page 22: ...alling the fitting insert the tip into the carburetor body Support the carburetor body with a wood block to avoid damage to other parts Use a bench vise or press to install the fitting squarely Press it in until it bottoms out diag 48 High and Low Speed Adjusting Screw Main Nozzle When reassembling position the coil spring on the adjusting screws followed by the small brass washer and the O ring s...

Page 23: ...event binding the long straight end of the clip should face the choke or air filter end of the carburetor as shown diag 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 inl...

Page 24: ...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 Primer Bulb To install start the retain...

Page 25: ...r 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 cont...

Page 26: ...vernor 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 shaf...

Page 27: ...ess or a vise Wipe the extra Loctite off after installation 5 Reassemble the washer s governor gear and spool followed by the retaining ring SHAFT RETAINING RING WASHER SHAFT GEAR ASSY GOV GEAR ASSY GOV WASHER SPACER WASHER SPOOL SHAFT 11 7 WASHER SHAFT SPOOL GEAR ASSY GOV RETAINING RING WASHER GEAR ASSY GOV RETAINING RING WASHER SPOOL SPACER RETAINING RING SPOOL RETAINING RING WASHER GEAR ASSY GO...

Page 28: ...ent 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 13 12 HIGH SPEED STOP OHH ...

Page 29: ...DJUST SPEED DECREASE INCREASE GOVERNED IDLE LINK AND ADJUSTMENT NOTE Early production OHH engines did not have governed idle set only the idle crack screw and high speed governor stop HIGH SPEED ADJUST Þ Þ 21 20 OH OHSK CONTROL OHSK OHM CONTROL GOVERNED HIGH SPEED ADJUST BEND GOVERNED HIGH SPEED ADJUST GOVERNED IDLE TAB GOVERNED IDLE SCREW Þ Þ INCREASE DECREASE T 10 THROTTLE CRACK SCREW T 10 THROT...

Page 30: ... 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 t...

Page 31: ...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 040 070 1 02 1 778 mm should exist at the gap location as illustrated This will assure that the carburetor will go into full choke when the control is placed in the start position NOTE Assure that the throttle cable has ful...

Page 32: ...s released the recoil spring turns the starter pulley in the opposite direction to retract the starter rope COMPONENTS 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 ...

Page 33: ... 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 str...

Page 34: ...TE DO NOT DRIVE THE CENTER PIN IN TOO FAR 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 pre load the recoil spring and thread the rope through the starter housing eyelet Pu...

Page 35: ...haft 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 pre load 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 th...

Page 36: ...minum starters is 115 to 135 in lbs 13 15 Nm diag 11 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 left hand knot should be tied on the end of the rope to secur...

Page 37: ...e 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 p...

Page 38: ...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 ar...

Page 39: ...ed 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 cor...

Page 40: ...ires 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...

Page 41: ...NO NO YES YES Internal engine failure or flywheel interference Repair or replace equipment causing excessive loading YES TROUBLESHOOTING ELECTRICAL STARTER CIRCUIT FLOW CHART Internal engine failure repair or replace engine Check valve lash Adjust if necessary Does the engine turn over without binding now Repair or replace electric starter Internal engine failure repair or replace engine NO Check ...

Page 42: ...switches or ammeter for breaks shorts Alternator coil failure replace coil assy 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 ...

Page 43: ...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 ...

Page 44: ...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 sy...

Page 45: ... 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...

Page 46: ... 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 sy...

Page 47: ...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 n...

Page 48: ...angeable diag 20 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 Keep the A C leads attached to the regulator rectifier Install the blower housing with the...

Page 49: ...ted during the check replace the regulator diag 23 FUEL SHUT DOWN SOLENOIDS If the engine is running the solenoid can be checked by removing the electrical plug in at the base of the solenoid Almost immediately the engine should shut down if not replace the solenoid Test the solenoid off the carburetor by applying 12 volt D C from the battery positive terminal to the or one solenoid terminal Conne...

Page 50: ...e 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 ...

Page 51: ...diag 29 30 GASKET ARMATURE THRUST WASHER BENDIX ASSEMBLY RETAINING RING DUST COVER RETAINER SPRING BRUSHES 31 29 ELECTRIC STARTER SERVICE 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 bu...

Page 52: ... 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 Not...

Page 53: ...rol 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...

Page 54: ...terlock 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 s...

Page 55: ...rminals 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 self tapping screws supplied with the new ...

Page 56: ... a resistance A large voltage from the module arcs the air gap which causes a spark and ignites the air fuel mixture in the cylinder diag 2 NOTE Always consult parts manual for correct plug and reach 1 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 wi...

Page 57: ...sconnect 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 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 f...

Page 58: ... out wire at the igniton module repeat test Check for proper air gap on ignition module and repeat test Test ignition module Check flywheel magnets for strength No Spark Test ignition module for intermittent or weak spark Check electric starter and battery if applicable Set proper air gap on ignition module Check flywheel and key for damage or sheared key Check for the correct spark plug FOUR CYCL...

Page 59: ...arbon Deposit Worn Oil Deposit When reinstalling the plug make sure it is clean of all foreign material 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...

Page 60: ...rocedure 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 correc...

Page 61: ...t takes to ignite all the available fuel the piston has moved to Top Dead Center TDC ready to take the full combustive force of the fuel for maximum power during downward piston travel The expanding gases force the piston down diag 3 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...

Page 62: ...l 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 CAMSHAFT GOVERNOR OIL DRAIN HOLE SPRAY MIST HOLE 5 COUNTERBALANCE SYSTEMS Some Tecumseh engine...

Page 63: ...es to exit The valves provide a positive seal when closed 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 ...

Page 64: ...on timing or incorrect spark plug Carbon in the combustion chamber 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 Oil level above full Wrong viscosity oil Engine cooling fins dirty causing overheating Breather damaged d...

Page 65: ...alance not properly aligned BREATHER PASSING OIL Oil level too high Breather damaged dirty or improperly installed Damaged gaskets seals or O rings Excessive RPM or improper governor setting Angle of operation too severe Piston rings not properly seated or ring end gaps are aligned LACKS POWER Air intake obstructed Lack or lubrication or improper lubrication Carburetor improperly adjusted Exhaust ...

Page 66: ...ettings 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 operat...

Page 67: ...he cause of weak compression worn rings leaking head gasket or leaking valves Follow the compression tester s procedure 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 O rings...

Page 68: ... 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...

Page 69: ...TE 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 ...

Page 70: ...ponents 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...

Page 71: ...ss 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...

Page 72: ...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 Valves are...

Page 73: ...n 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 cyl...

Page 74: ...er 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 Insp...

Page 75: ...OMPRESSION RELEASE SPRING COMPRESSION RELEASE A B 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 requi...

Page 76: ...es 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 375o 400o F 1900 2040 C CAUTION USE PROTECTION FOR EYES AND HANDS BE CAREFUL THE HOT OIL AND HEAD CAN EASILY CAUSE BURNS 3 Us...

Page 77: ...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 ...

Page 78: ...VER 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 instal...

Page 79: ...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 stagge...

Page 80: ...lunger style oil pump chamfered side toward the gear if applicable ultra balance shaft or dual balance shafts if applicable Align the timing mark or notched tooth on the crankshaft gear to the mark or hole in the camshaft gear If equipped time the Ultra balance with the piston at Top Dead Center T D C Slide the drive gear over the keyway in crankshaft while aligning the timing marks on the gears a...

Page 81: ...t surface For models OHH and OVRM install the springs dampening coils toward the head and retainers on the valves and use fingers to compress the springs until the notch in the retainer is located in the notch in the valve stem Repeat the procedure for other valve 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 ...

Page 82: ... 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 o rings white o ring on the exhaust guide followed by valve spring caps valve springs with the dampening coils toward the head ...

Page 83: ...rt 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...

Page 84: ...up 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 flyw...

Page 85: ...vice 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 t...

Page 86: ...XL120 202034E 143 426152 OVXL120 202039E 143 426172 OVXL125 202067E 143 436032 OHV125 203013A 143 436042 OHV125 203012A 143 436092 OHV125 203015A 143 436102 OHV125 203018A 143 436132 OHV125 203020A 143 436152 OHV125 203023A 143 796112 OHSK120 222005 143 806062 OHSK120 222005A 143 816042 OHSK120 222007B 143 836052 OHSK120 222015C 143 941200 OHV125 203023B 143 941201 OHSK120 222015D 143 951600 OHV16...

Page 87: ...5 375 Crankshaft Dia 9985 25 362 1 0005 25 413 1 0005 25 413 9985 25 362 P T O Main Brg 9990 25 375 1 0010 25 425 1 0010 25 425 9990 25 375 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 Pis...

Page 88: ...rg 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 Clearan...

Page 89: ... a e H r e d n i l y C 0 3 2 9 1 6 2 X X X X X X s t l o B d o R n n o C 5 0 1 2 1 X X s t l o B d o R n n o C 0 2 2 3 8 1 8 4 2 X X X X e g n a l F r o r e v o C l y C 5 1 1 5 9 3 1 X X e g n a l F r o r e v o C l y C 5 2 1 5 0 1 4 1 X X X X t u N l e e h w y l F 0 5 4 5 3 1 5 X X n o r I t s a C t u N l e e h w y l F 0 5 5 6 4 2 6 X t u N l e e h w y l F 0 0 7 8 5 9 7 X X X X g u l P k r a p S 0...

Page 90: ... i o c e R 0 5 5 5 X X X r e t r a t S l i o c e R 0 4 5 4 X r e t r a t S l i o c e R 0 8 9 X X X X r e d n i l y C o t r e t r a t S c i r t c e l E 0 0 1 1 1 X X X X r e d n i l y C o t r e t r a t S c i r t c e l E 0 5 1 5 2 1 7 1 X X t u N m a J x e H m r A r e k c o R 8 1 2 X 1 X n e l l A k c o L m r A r e k c o R w e r c S 5 7 5 8 X t u N m a J g n i t s u j d A r e k c o R 0 3 1 8 0 1 7 4...

Page 91: ...eries transaxles This video will show a complete step by step procedure for teardown and reassembly of the 900 910 and 920 series transaxles 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 in depth look at the 800 series transaxles Detailing the...

Page 92: ...KIT 670195E Kit contains tools for 2 and 4 cycle engines Includes all items on this page but items may be purchased separately www mymowerparts com For Discount Tecumseh Engine Parts Call 606 678 9623 or 606 561 4983 ...

Page 93: ...er for recessed seal position No 670330 1 1 2 extended camshaft No 670335 1 1 8 crankshaft bearing diameters No 670336 1 1 8 crankshaft bearing diameter recessed seal No 670337 1 to be used with 670265 and 670266 recessed and raised FLYWHEEL KNOCK OFF TOOL No 670103 Knock off tool right hand 7 16 No 670169 Knock off tool right hand 1 2 No 670314 Knock off tool right hand 5 8 No 670329 Knock off to...

Page 94: ...d OHV11 16 5 Intake and Exhaust Oversize diameter 3432 3442 8 717 8 743 mm BUSHING TOOL KIT Rebushing tool kit for use on OHM OHSK110 120 OVM OHV11 13 AND OVXL 1 3 8 main bearing A None B None C No 670311 Bushing Driver Installer No 670317 Bushing Driver Installer OVRM AND OHV11 16 5 SPEED ADJUSTMENT TOOL No 670326 TORX DRIVERS Torx 8 670334 Torx 10 670333 Torx 15 670323 Torx 20 670324 Torx 25 670...

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