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Troubleshooting
Problem: Engine will not start or is hard to start (Compression too low)
Condition
1. Valve clearance out of adjustment
2. Valve guides worn
3. Valve timing incorrect
4. Piston rings worn excessively
5. Cylinder bore worn
6. Spark plug seating poorly
7. Starter motor cranks too slowly - does not turn
Problem: Engine will not start or is hard to start (No spark)
Condition
1. Spark plug fouled
2. Spark plug wet
3. Magneto defective
4. ECM defective
5. Ignition coil defective
6. High-tension lead open - shorted
Problem: Engine will not start or is hard to start (No fuel reaching the throttle body
Condition
1. Gas tank vent hose obstructed
2. Fuel hose obstructed
3. Fuel screens obstructed
4. Fuel pump defective
Problem: Engine stalls easily
Condition
1. Spark plug fouled
2. Magneto defective
3. ECM defective
4. Valve clearance out of adjustment
Problem: Engine noisy (Excessive valve chatter)
Condition
1. Valve clearance excessive
2. Valve spring(s) weak - broken
3. Rocker arm - rocker arm shaft worn
4. Camshaft worn
5. Valve tappets worn
Problem: Engine noisy (Noise seems to come from piston)
Condition
1. Piston - cylinder worn
2. Combustion chamber carbon buildup
3. Piston pin bore worn
4. Piston pin worn
5. Piston rings - ring groove(s) worn
Problem: Engine noisy (Noise seems to come from timing chain)
Condition
1. Chain stretched
2. Sprockets worn
3. Tension adjuster malfunctioning
Problem: Engine noisy (Noise seems to come from crankshaft)
Condition
1. Bearing worn - burned
2. Lower rod-end bearing worn - burned
3. Connecting rod side clearance too large
Remedy
1. Adjust clearance
2. Replace cylinder head
3. Correct valve timing - check chain, sprockets, and cam chain
tensioner
4. Replace rings
5. Replace cylinder
6. Tighten plug
7. Check - replace starter motor
Remedy
1. Clean - replace plug
2. Clean - dry plug
3. Replace stator coil
4. Replace ECM
5. Replace ignition coil
6. Replace high tension lead
Remedy
1. Clean vent hose
2. Clean - replace hose
3. Clean - replace inlet screen - valve screen
4. Replace fuel pump
Remedy
1. Clean plug
2. Replace stator coil
3. Replace ECM
4. Adjust clearance
Remedy
1. Adjust clearance
2. Replace spring(s)
3. Replace arm - shaft
4. Replace camshaft
5. Replace tappets
Remedy
1. Replace - service piston - cylinder
2. Clean chamber
3. Replace piston
4. Replace piston pin
5. Replace rings - piston
Remedy
1. Replace chain
2. Replace sprockets
3. Repair - replace adjuster
Remedy
1. Replace bearing
2. Replace crankshaft
3. Replace crankshaft
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Table of Contents
Troubleshooting
