3-6
Problem: Engine runs poorly at high speed
Condition Remedy
1. High RPM “cut out” against RPM limiter
2. Valve springs weak
3. Valve timing out of adjustment
4. Cams - rocker arms - tappets worn
5. Spark plug gap too narrow
6. Ignition coil defective
7. Float level too low
8. Air cleaner element obstructed
9. Fuel hose obstructed
10. Fuel pump defective
1. Shift into higher gear - decrease speed
2. Replace springs
3. Adjust timing
4. Replace cams - arms - tappets
5. Adjust gap
6. Replace ignition oil
7. Adjust float height
8. Clean element
9. Clean or replace hose
10. Replace fuel pump
Problem: Exhaust smoke dirty or heavy
Condition Remedy
1. Oil (in the engine) overfilled - contaminated
2. Piston rings - cylinder worn
3. Valve guides worn
4. Cylinder wall scored - scuffed
5. Valve stems worn
6. Stem seals defective
1. Drain excess oil - replace oil
2. Replace - service rings - cylinder
3. Replace cylinder head
4. Replace - service cylinder
5. Replace valves
6. Replace seals
Problem: Engine lacks power
Condition Remedy
1. Valve clearance incorrect
2. Valve springs weak
3. Valve timing incorrect
4. Piston ring(s) - cylinder worn
5. Valve seating poor
6. Spark plug fouled
7. Rocker arms - shafts worn
8. Spark plug gap incorrect
9. Carburetor jets obstructed
10. Float level out of adjustment
11. Air cleaner element obstructed
12. Oil (in the engine) overfilled - contaminated
13. Intake manifold leaking air
14. Cam chain worn
1. Adjust clearance
2. Replace springs
3. Re-time valve gear
4. Replace - service rings - cylinder
5. Repair seats
6. Clean - replace plug
7. Replace arms - shafts
8. Adjust gap - replace plug
9. Clean jets
10. Adjust float height
11. Clean element
12. Drain excess oil - change oil
13. Tighten - replace manifold
14. Replace cam chain
Problem: Engine overheats
Condition Remedy
1. Carbon deposit (piston crown) excessive
2. Oil low
3. Octane low - gasoline poor
4. Oil pump defective
5. Oil circuit obstructed
6. Gasoline level (in float chamber) too low
7. Intake manifold leaking air
8. Fan malfunctioning
9. Fan switch malfunctioning
1. Clean piston
2. Add oil
3. Drain - replace gasoline
4. Replace pump
5. Clean circuit
6. Adjust float height
7. Tighten - replace manifold
8. Check fan fuse - replace fan
9. Replace fan switch
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