Problem: Engine runs poorly at high speed
Condition Remedy
1. High RPM "cut out" against RPM limiter 1. Shift into higher gear - decrease speed
2. Valve springs weak 2. Replace springs
3. Valve timing out of adjustment 3. Adjust timing
4. Cams - rocker arms - tappets worn 4. Replace cams - arms - tappets
5. Spark plug gap too narrow 5. Adjust gap
6. Ignition coil defective 6. Replace ignition oil
7. Float level too low 7. Adjust float height
8. Air cleaner element obstructed 8. Clean element
9. Fuel hose obstructed 9. Clean or replace hose
10. Fuel pump defective 10. Replace fuel pump
Problem: Exhaust smoke dirty or heavy
Condition Remedy
1. Oil (in the engine) overfilled - contaminated 1. Drain excess oil - replace oil
2. Piston rings - cylinder worn 2. Replace - service rings - cylinder
3. Valve guides worn 3. Replace cylinder head
4. Cylinder wall scored - scuffed 4. Replace - service cylinder
5. Valve stems worn 5. Replace valves
6. Stem seals defective 6. Replace seals
Problem: Engine lacks power
Condition Remedy
1. Valve clearance incorrect 1. Adjust clearance
2. Valve springs weak 2. Replace springs
3. Valve timing incorrect 3. Re-time valve gear
4. Piston ring(s) - cylinder worn 4. Replace - service rings - cylinder
5. Valve seating poor 5. Repair seats
6. Spark plug fouled 6. Clean - replace plug
7. Rocker arms - shafts worn 7. Replace arms - shafts
8. Spark plug gap incorrect 8. Adjust gap - replace plug
9. Carburetor jets obstructed 9. Clean jets
10. Float level out of adjustment 10. Adjust float height
11. Air cleaner element obstructed 11. Clean element
12. Oil (in the engine) overfilled - contaminated 12. Drain excess oil - change oil
13. Intake manifold leaking air 13. Tighten - replace manifold
14. Cam chain worn 14. Replace cam chain
Problem: Engine overheats
Condition Remedy
1. Carbon deposit (piston crown) excessive 1. Clean piston
2. Oil low 2. Add oil
3. Octane low - gasoline poor 3. Drain - replace gasoline
4. Oil pump defective 4. Replace pump
5. Oil circuit obstructed 5. Clean circuit
6. Gasoline level (in float chamber) too low 6. Adjust float height
7. Intake manifold leaking air 7. Tighten - replace manifold
8. Fan malfunctioning 8. Check fan fuse - replace fan
9. Fan switch malfunctioning 9. Replace fan switch
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4.7 / 5