Troubleshooting Problem: Engine will not start or is hard to start (Compression too low) Condition Remedy 1. 2. 3. 4. 5. 6. 7.
Valve clearance out of adjustment Valve guides worn — seated poorly Valves mistimed Piston rings worn excessively Cylinder bore worn Spark plug seating poorly Starter motor cranks too slowly - does not turn
Problem: Engine will not start or is hard to start (No spark) Condition 1. 2. 3. 4. 5. 6.
Spark plug fouled Spark plug wet Magneto defective CDI unit defective Ignition coil defective High-tension lead open — shorted
1. 2. 3. 4. 5. 6. 7.
Adjust clearance Repair — replace guides Adjust valve timing Replace rings Replace cylinder Tighten plug See Starter Motor
Remedy 1. 2. 3. 4. 5. 6.
Clean — replace plug Clean — dry plug Replace magneto Replace CDI unit Replace ignition coil Replace high tension lead
Problem: Engine will not start or is hard to start (No fuel reaching the carburetor) Condition Remedy 1. 2. 3. 4.
Gas tank vent hose obstructed Carburetor inlet needle defective Fuel hose obstructed Fuel screens obstructed
Problem: Engine stalls easily Condition 1. 2. 3. 4. 5.
Spark plug fouled Magneto defective CDI unit defective Carburetor jets obstructed Valve clearance out of adjustment
Problem: Engine noisy (Excessive valve chatter) Condition 1. 2. 3. 4.
Valve clearance too large Valve spring(s) weak — broken Rocker arm — rocker arm shaft worn Camshaft worn
Problem: Engine noisy (Noise seems to come from piston) Condition 1. 2. 3. 4.
Piston — cylinder worn Combustion chamber carbon buildup Piston pin — piston pin bore worn Piston rings — ring groove(s) worn
1. 2. 3. 4.
Clean vent hose Replace needle Clean — replace hose Clean — replace inlet screen - valve screen
Remedy 1. 2. 3. 4. 5.
Clean plug Replace magneto Replace CDI unit Clean jets Adjust clearance
Remedy 1. 2. 3. 4.
Adjust clearance Replace spring(s) Replace arm — shaft Replace camshaft
Remedy 1. 2. 3. 4.
Replace — service piston — cylinder Clean chamber Replace — service pin — bore Replace rings — piston
Problem: Engine noisy (Noise seems to come from timing chain) Condition Remedy 1. Chain stretched 2. Sprockets worn 3. Tension adjuster malfunctioning
1. Replace chain 2. Replace sprockets 3. Repair — replace adjuster
Problem: Engine noisy (Noise seems to come from crankshaft) Condition Remedy 1. Bearing worn — burned 2. Lower rod-end bearing worn — burned 3. Connecting rod side clearance too large
1. Replace bearing 2. Replace bearing 3. Replace thrust washer(s)
Problem: Engine noisy (Noise seems to come from transmission) Condition Remedy 1. 2. 3. 4. 5.
Gears worn — rubbing Splines worn Primary gears worn — rubbing Bearings worn Bushing worn
1. 2. 3. 4. 5.
Replace gears Replace shaft(s) Replace gears Replace bearings Replace bushing
Problem: Engine noisy (Noise seems to come from secondary-transmission/right-side cover) Condition Remedy 1. Gears — shaft(s) worn 2. Bearing(s)/bushing(s) damaged
Problem: Centrifugal clutch slipping Condition 1. Clutch shoes worn 2. Clutch housing excessively worn 3. Drive belt slipping — worn
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1. Replace gears — shafts 2. Replace bearing(s)/bushing(s)
Remedy 1. Replace shoes 2. Replace clutch housing 3. Replace drive belt
