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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. Check wiring, connections, fuses, ignition or starter switch, safety switches, or solenoid for continuity

using a ohmmeter or a continuity light. Repair or replace as necessary.

4. Remove all equipment loads from the engine. Take off all drive belts, chains, and couplers to isolate

the engine from the equipment it is powering.

5. Try to turn the engine over using the recoil assembly if equipped. If the engine doesnt turn over, a

mechanical binding may be the cause. Check for proper lubrication (oil level and viscosity) and check

for electric starter gear and flywheel ring gear interference. If no problem is discovered, the problem is

an internal failure.

6. If the engine binds only on the compression stroke, check the engine valve clearance per the

specification table in Chapter 10. If the valve clearance is within the specifications, the camshaft

(compression release failure) may require replacement. Valve clearance not within the listed

specifications will require resetting the rocker arms to obtain the proper clearance.

7. If the engine turns over freely, the electric starter should be replaced or disassembled and checked.

See "Service" in this chapter. 120 volt starters labeled UL Listed/CSA Approved can be serviced;

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

"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 on

the engine. Consult a Tecumseh dealer or a parts manual to identify the charging system. To make many of the

tests it is necessary to run the engine and measure alternator output with a voltmeter. When making voltage

tests with the engine running, it is not necessary to take readings at all the listed R.P.M.s. Checking at one of

the speeds is sufficient.

BATTERY GROUND (BL)

ELECTRIC STARTER

LEAD (ORG)

BLACK

RED

(-) ENGINE GROUND

(+) POSITIVE LEAD

MAGNETO GROUND

(GR)

D.C. OUTPUT

LEAD (RED)

In some cases an open circuit D.C. check cannot be

made. A SCR (Silicon Controlled Rectifier) is located

in the circuit which requires a minimum turn on

voltage to allow it to conduct. Without the battery in

the circuit this turn on voltage is not present. The

SCR senses this and there will be no D.C. output

from the regulator / rectifier.
Each charging system has its own testing procedure.

Test the charging system using the applicable

procedure found on the following pages.

350 Milliamp Charging System

CHECKING THE SYSTEM:

The battery must be in

the circuit to perform the test properly. Set the

voltmeter to the 0 - 20 D.C. volt scale. Connect a

voltmeter across the battery. The voltmeter should

read the battery voltage. Start the engine. With the

engine running, there should be an increase in the

voltage reading. If there is no change in the voltage

reading, the alternator is defective and should be

replaced. See Chapter 9 for "Disassembly Procedure"

(diag. 7).

Содержание OHH50 - 65

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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...

Страница 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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