Tecumseh OHH50 - 65 Handbook Download Page 65

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ENGINE OPERATION PROBLEMS

ENGINE MISFIRES

Improper Valve Lash

Weak valve spring

Excessive carbon build up

Carburetor improperly adjusted

Ignition timing or

incorrect spark plug

Valves sticking or not seating properly

Wrong or fouled spark plug

Bent crankshaft

ENGINE VIBRATES EXCESSIVELY

Attached equipment out of balance

Loose mounting bolts

If applicable counter balance 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 Obstructed

Improper valve lash

Loss of compression (worn rings,

blown head gasket)

Summary of Contents for OHH50 - 65

Page 1: ...L120 OVXL125 Other illustrated Tecumseh 2 Cycle Engine 4 Cycle Engine and Transmission manuals booklets and wall charts are available through Tecumseh For complete listing write or call CONTAINS SEARS...

Page 2: ...UEL INLET FITTING 19 HIGH AND LOW SPEED ADJUSTING SCREW MAIN NOZZLE 19 INLET NEEDLE AND SEAT 20 FLOAT INSTALLATION 20 FUEL BOWL AND BOWL NUT 21 IMPULSE FUEL PUMP 21 PRIMER BULB 21 FINAL CHECKS 21 CHAP...

Page 3: ...N 58 OPERATION 58 4 CYCLE ENGINE THEORY 58 LUBRICATION SYSTEMS 59 COUNTERBALANCE SYSTEMS 59 COMPONENTS 60 ENGINE OPERATION PROBLEMS 61 ENGINE OPERATION PROBLEMS 62 TESTING 63 ENGINE KNOCKS 63 ENGINE O...

Page 4: ...te a variation to the basic engine specification 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 follow...

Page 5: ...performance Fuel should not be stored in an engine or container more than 30 days prior to use This time may be extended with the use of a fuel stabilizer like TECUMSEH S part number 730245 See STORA...

Page 6: ...life Always check fuel as a primary cause of poor engine performance The following is a minor tune up procedure When this procedure is completed the engine should operate governor springs or linkage...

Page 7: ...at the carburetor or fuel tank Be careful not to damage the fuel line fittings or fuel tank 2 Drain the carburetor by pressing upward on bowl drain if equipped which is located on the bottom of the ca...

Page 8: ...t 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 compone...

Page 9: ...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 wil...

Page 10: ...e cleaner must not be oiled Clean the air cleaner 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...

Page 11: ...choke shutter is closed and the only air entering 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...

Page 12: ...reated by the up and down movement of the piston A hose called a pulse line connects the fuel pump diaphragm chamber to the crankcase and transmits the impulses to the pump diaphragm The impulses actu...

Page 13: ...or is a Series 3 or Series 4 look at the throttle end of the carburetor Series 3 will have one throttle plate screw diag 10 The Series 4 will have two throttle plate screws diag 11 Series 7 Series 7 c...

Page 14: ...cing should be done by a Authorized Tecumseh 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...

Page 15: ...With the spark plug removed and a shop towel over the spark plug hole turn the engine over slowly 3 or 4 times to remove excess gasoline from the engine cylinder CAUTION KEEP ALL COMBUSTIVE SOURCES A...

Page 16: ...to warm up to normal operating temperature 3 5 minutes Set the speed control to the HIGH or FAST position then turn the main mixture adjustment screw in clockwise slowly until the engine begins to ru...

Page 17: ...ing it with an ice pick or similar instrument then remove the jet for service always replace the cap 3 Note the position of the spring clip on the inlet needle and float Remove the float hinge pin wit...

Page 18: ...ghtly smaller than the jet drive the jet through and into the center leg Insert the high altitude jet in the same hole Using a punch slightly larger than the diameter of the new jet tap it into place...

Page 19: ...l to its original position and tighten the bowl nut THE TECUMSEH SERIES 7 AND THE WALBRO MODEL LMK CARBURETOR HAVE A FIXED AND NONADJUSTABLE FLOAT HEIGHT Inspection After careful disassembly of the ca...

Page 20: ...ivery problems are experienced flooding or starvation Sealing problems with the inlet needle seat may not be visible and replacement is recommended Only the inlet needle is serviceable on the Walbro m...

Page 21: ...if equipped If binding occurs correct by loosening the screws and repositioning throttle plate Always use a new screw s when reinstalling the throttle shutter to prevent the screws from loosening and...

Page 22: ...released diag 47 Fuel Inlet Fitting When installing 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...

Page 23: ...he float tab by means of a spring clip To prevent binding the long straight end of the clip should face the choke or air filter end of the carburetor as shown diag 52 Float Installation On Series 7 ca...

Page 24: ...the pump Make sure fuel is available in both fuel tanks and the original fuel tank s fuel line is connected to the fuel pump inlet Place the pump outlet line in a proper draining receptacle With the...

Page 25: ...pable of maintaining a constant R P M with or without an engine load Engine overspeeding must be corrected immediately before serious engine damage occurs Use the applicable following procedure to dia...

Page 26: ...r Gear or Shaft Replacement Upset Style Governor Shaft 1 Grip the original spool in a vise and use a twisting and pulling motion on the flange until the spool is free 2 Clamp the shaft in a vise and p...

Page 27: ...overnor shaft to the proper depth using a press or a vise Wipe the extra Loctite off after installation 5 Reassemble the washer s governor gear and spool followed by the retaining ring SHAFT RETAINING...

Page 28: ...H REMOTE SPEED CONTROL The engine and equipment control must be adjusted to allow the engine control lever to touch the high speed stop when the equipment control is set in the highspeed or fast posit...

Page 29: ...LICATION CONTROL HIGH SPEED ADJUSTMENT BEND TO ADJUST SPEED DECREASE INCREASE GOVERNED IDLE LINK AND ADJUSTMENT NOTE Early production OHH engines did not have governed idle set only the idle crack scr...

Page 30: ...e alignment of the lever bushing and washers to ensure that everything is aligned properly and torque the lock nut to 20 in lbs 2 Nm The control lever should move freely This engine speed control is s...

Page 31: ...ing bracket Place a pin through the two holes place the equipment throttle control to the wide open position hook the bowden cable end in the control as shown and tighten the cable housing clamp In th...

Page 32: ...isengaged position When the starter handle is released the recoil spring turns the starter pulley in the opposite direction to retract the starter rope COMPONENTS SERVICE Starter related problems will...

Page 33: ...e decal or plastic disc in the center of the rewind 3 Place a 1 25 4 mm deep well socket under the retainer Set the rewind on a bench supported on the socket 4 Use a 5 16 7 937 mm or a 1 4 6 35 mm pun...

Page 34: ...in 1 8 3 175 mm of the top of the starter NOTE 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 cente...

Page 35: ...until the leg prongs pop out of the center shaft 7 Turn the starter over and snap the locking tab between the retainer legs replace the top decal NOTE Refer to Service Bulletin 122 for metal locking t...

Page 36: ...rill bit The center screw torque on cast aluminum 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 th...

Page 37: ...he pulley on the housing center leg align the end of recoil spring and the notch in the pulley and push down until seated 3 Insert the starter dogs on the pulley pegs with the flat side away from the...

Page 38: ...rrent running through the armature windings The armature magnetism repels the magnetism produced by the permanent field magnets of the electric starter The repelling magnetic forces cause the armature...

Page 39: ...es and testing procedure WIRING The wires used in Tecumseh electrical systems are copper stranded with an insulated coating around the copper strands CONDITION All wiring must be fully insulated betwe...

Page 40: ...ECTIFIERS and DIODES Charging a battery requires that the alternating current produced by the alternator be changed to direct current This is accomplished by using a diode or rectifier REGULATOR RECTI...

Page 41: ...g does engine bind on compression stroke NO NO NO YES YES Internal engine failure or flywheel interference Repair or replace equipment causing excessive loading YES TROUBLESHOOTING ELECTRICAL STARTER...

Page 42: ...AL CHARGING CIRCUIT FLOW CHART Check wiring switches or ammeter for breaks shorts Alternator coil failure replace coil assy Identify the charging system used by model and specification number or visua...

Page 43: ...d however starters labeled CSA must only be replaced If the preceding steps fail to correct the problem the engine will require to be disassembled to find the mechanical failure See Chapter 9 under Di...

Page 44: ...should read 2500 R P M 8 0 Volts A C 3000 R P M 9 5 Volts A C 3300 R P M 10 5 Volts A C 3600 R P M 11 5 Volts A C It the above minimum readings are noted the alternator is okay Check for defective lig...

Page 45: ...n the alternator side of the diode Test the A C voltage before the diode using an A C voltmeter With the engine running minimum values should read 2500 R P M 18 0 Volts A C 3000 R P M 22 0 Volts A C 3...

Page 46: ...pter 9 for Disassembly Procedure 3 Amp D C 5 Amp A C Alternator This unit combines a 3 Amp D C system used to charge a battery with a 5 Amp A C system used for lighting Located in the red wire of the...

Page 47: ...s D C 5 Amp A C Yellow wire 2500 R P M 15 0 Volts A C 3000 R P M 18 0 Volts A C 3600 R P M 22 0 Volts A C If the above minimum values are noted the system is okay Check for defective lights wiring or...

Page 48: ...ame However regulator styles are not interchangeable 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 pr...

Page 49: ...D C or the proper minimum A C voltage is noted 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...

Page 50: ...housing and disconnect the LOS lead from the ignition module Reinstall the blower housing and spin the engine over If spark occurs now replace the LOS switch If no spark is seen replace the ignition...

Page 51: ...i 700 bar an internal engine problem exists diag 29 30 GASKET ARMATURE THRUST WASHER BENDIX ASSEMBLY RETAINING RING DUST COVER RETAINER SPRING BRUSHES 31 29 ELECTRIC STARTER SERVICE This section cover...

Page 52: ...the starter terminal post 2 Remove the nuts holding the end cap in place Remove the end cap and the thrust washer 3 Grasp the thru bolts using a vise grip positioned as close to the flanged end as po...

Page 53: ...he operator lets go of the engine blade control bail at the operator position and the engine is stopped Tecumseh s flywheel brake system provides consumer safety by killing the engine and stopping the...

Page 54: ...ule from firing the spark plug diag 3 The interlock switch is a push button switch that is activated by the brake lever when the engine blade control is actuated If there is a electric starter switch...

Page 55: ...k Continuity should exist between the two terminals when the interlock switch button is completely depressed No continuity should exist when the button is released If the switch fails replace the swit...

Page 56: ...wo are separated by an air gap which creates a resistance A large voltage from the module arcs the air gap which causes a spark and ignites the air fuel mixture in the cylinder diag 2 NOTE Always cons...

Page 57: ...er as in step 1 Remove the blower housing disconnect the ignition grounding lead at the ignition module Reinstall the blower housing and crank the engine over If spark occurs check the ignition switch...

Page 58: ...grounds in wiring Disconnect ignition ground 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 stre...

Page 59: ...ton rings 10 Weak ignition system 6 Normal Carbon 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 MICROS...

Page 60: ...hapter 9 under Service for the disassembly procedure 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...

Page 61: ...igniting the air fuel mixture In the time it 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 d...

Page 62: ...mshaft rotates the eccentric moves the barrel back and forth on the plunger forcing oil through the hole in the center of the camshaft The ball on the end of the plunger is anchored in a recess in the...

Page 63: ...ixture to enter the cylinder and exhaust gases 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 v...

Page 64: ...erly adjusted or improper RPM setting Ignition timing or incorrect spark plug Carbon in the combustion chamber Dirty carburetor or air filter Carburetor improperly adjusted Governor sticking binding o...

Page 65: ...Loose mounting bolts If applicable counter balance not properly aligned BREATHER PASSING OIL Oil level too high Breather damaged dirty or improperly installed Damaged gaskets seals or O rings Excessiv...

Page 66: ...her tachometer and compare it to the R P M settings found on microfiche card 30 according to the engine model and specification number Adjust as necessary 6 Check the ignition timing See Chapter 8 Ign...

Page 67: ...the engine has weak compression determine the cause of weak compression worn rings leaking head gasket or leaking valves Follow the compression tester s procedure EXCESSIVE OIL CONSUMPTION 1 Check th...

Page 68: ...ace hammer loosening the plastic tank wedges in the blower housing slots 5 Remove the blower housing by first unscrewing the screw holding the dipstick tube to the blower housing and removing the rema...

Page 69: ...emove the head bolts head and head gasket NOTE ON SOME OHV ENGINES THE EXHAUST PUSH ROD CAN ONLY BE REMOVED AFTER THE HEAD IS OFF YOU MUST HAVE IT BACK IN BEFORE RE ASSEMBLY On engine models OHM OHSK1...

Page 70: ...crankshaft gears and remove the internal components diag 20 18 Remove the lifters rod cap and counterbalance shaft or gears if applicable 19 Before removing the piston remove any carbon from the top o...

Page 71: ...mmends 380 grit for finish in a standard cross hatch Start with coarse stones and center the cylinder under the drill press spindle Lower the hone so the lower end of the stones contacts the lowest po...

Page 72: ...iston should be at T D C on the compression stroke both valves closed See specification section When servicing the valves all carbon should be removed from the valve head and stem If the valves have b...

Page 73: ...feeler gauge The ring end gap must be within the specification to have adequate oil control diag 29 This procedure will assure correct piston ring end gap measurement Ring side clearance should also...

Page 74: ...the crankshaft visually and with a micrometer for wear scratching scoring or out of round condition at the bearing surfaces Check for bends on the P T O end using a straight edge square or a dial ind...

Page 75: ...asier 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 cons...

Page 76: ...eplacement 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 o...

Page 77: ...h 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 clea...

Page 78: ...ARE NOT POSITIONED FLUSH TO THE CYLINDER COVER ATTEMPTING TO INSTALL THE SEAL TOO FAR IN CAN CAUSE DAMAGE TO THE OIL SEAL AND ENGINE If the crankshaft is removed from the engine remove the old oil se...

Page 79: ...all internal engine parts with solvent and blow dry with compressed air or allow to dry 2 Using the correct seal protector see Chapter 11 under Tools apply engine oil to the crankshaft bearing surfac...

Page 80: ...7 Install the lifters camshaft barrel and plunger 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...

Page 81: ...their seats while placing the head on a flat 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 un...

Page 82: ...at and hold the valve in this position Use a 12 inch 30 5 cm piece of fuel line and wedge one end on each side of the valve stem through the port opening to hold the valve e Bolt the valve spring comp...

Page 83: ...piston at T D C and both valves closed Insert the specified feeler gauge between the rocker arm and valve stem Adjust until a slight sliding drag is felt On models OHH and OVRM lock this position by...

Page 84: ...f applicable flywheel key flywheel starter cup if applicable bevelled washer concave surface in and flywheel nut Use strap wrench part 670305 to hold the flywheel and tighten the nut to the specified...

Page 85: ...tanks have a fuel filter in the tank and service is not necessary 24 Fill the engine with oil to the full mark on the dipstick Add fresh fuel to the fuel tank and secure the cap 25 Install the spark p...

Page 86: ...62E 143 426122 OVXL125 202064E 143 426142 OVXL120 202034E 143 426152 OVXL120 202039E 143 426172 OVXL125 202067E 143 436032 OHV125 203013A 143 436042 OHV125 203012A 143 436092 OHV125 203015A 143 436102...

Page 87: ...g 9990 25 375 9990 25 375 9990 25 375 9990 25 375 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 Cra...

Page 88: ...50 34 925 1 6250 41 275 Conn Rod Dia Crank Brg 1 0005 25 413 1 3775 34 988 1 3775 34 988 1 6234 41 234 1 0010 25 425 1 3780 35 001 1 3780 35 001 1 6240 41 250 Camshaft Bearing Diameter 4970 12 624 623...

Page 89: ...7 1 5 1 V H O s e i r e S 4 0 2 s t l o B d 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...

Page 90: ...r a t S l i o c e R 5 2 3 X r e t r a t S l 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...

Page 91: ...695148 Teardown and reassembly of the 900 series transaxles This video will show a complete step by step procedure for teardown and reassembly of the 900 910 and 920 series transaxles 695185 Electric...

Page 92: ...89 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...

Page 93: ...08 No 670310 1 3 8 crankshaft bearing diameter 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 rec...

Page 94: ...No 670284 Used on OVXL OVM OHM120 OVXL125 and 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 O...

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