Complaint Symptom and possible causes Remedy
Engine runs
poorly in
high-speed
range.
1. Excessively worn cylinder or piston rings.
2. Stiff piston ring in place.
3. Spark plug gaps to narrow.
4. Ignition not advanced sufficiently due to poorly working CDI & ignition coil unit.
5. Defective magneto stator coil.
6. Float-chamber fuel level too low.
7. Clogged air cleaner element.
8. Clogged fuel hose, resulting in inadequate fuel supply to carburetor.
9. Clogged fuel cock vacuum pipe.
Replace.
Replace.
Adjust.
Replace.
Replace.
Adjust or replace.
Clean.
Clean and prime.
Clean.
Dirty or heavy
exhaust smoke.
1. Too much engine oil to the engine.
2. Use of incorrect engine oil.
Check oil pump.
Change.
Engine lacks
power.
1. Excessively worn cylinder or piston rings.
2. Stiff piston rings in place.
3. Gas leaks from crankshaft oil seal.
4. Spark plug gaps incorrect.
5. Clogged air cleaner element.
6. Float-chamber fuel level out of adjustment.
7. Clogged air cleaner element.
8. Fouled spark plug,
9. Sucking air from intake pipe.
10. Slipping or worn V-belt.
11. Damaged/worn rollers in the movable drive face.
12. Weakened movable driven face spring.
13. Too rich fuel/air mixture due to defective starter system.
Replace.
Replace.
Replace.
Adjust or replace.
Clean.
Adjust or replace.
Clean.
Clean or replace.
Retighten or replace.
Replace.
Replace.
Replace.
Replace.
Engine
overheats.
1. Heavy carbon deposit on piston crown.
2. Defective oil pump or clogged oil circuit.
3. Fuel level too low in float chamber.
4. Air leakage from intake pipe.
5. Use of incorrect engine oil.
6. Use lf improper spark plug.
7. Clogged exhaust pipe/muffler.
Clean.
Replace and clean.
Adjust or replace.
Retighten or replace.
Change.
Change.
Clean or replace.
CARBURETOR
Complaint Symptom and possible causes Remedy
Trouble with
starting.
1. Starter jet is clogged.
2. Air leaking from a joint between starter body and carburetor.
3. Air leaking from carburetor′s joint or vacuum hose joint.
4. Starter plunger is not operating properly.
Clean.
Check starter body and
carburetor for tightness, and
replace gasket.
Check and replace.
Check and replace.
Idling or
low-speed
troubles.
1. Pilot jet, pilot air jet are clogged or loose.
2. Air leaking from carburetor′s joint, vacuum pipe joint, or
starter.
3. Pilot outlet is clogged.
4. Starter plunger is not fully close.
Check and clean.
Check and replace.
Check and clean.
Check and replace.
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