Overheat; Low Coolant Level - Yamaha YTZ250S 1986 Service Manual

Overheat
Possible Cause Remedy
1.
Incorrect air-fuel mixture
• Adjust
2.
Air leaks through carburetor joint.
• Replace or replace
3. Incorrect ignition timing
• Adjust
4.
Carbon builds up in cylinder head
• Decarbonize
or on piston head.
5. Improper spark plug heat range
• Replace
(too hot)
6. Fuel is deteriorated or oil-gas
• Replace
mixing ratio is incorrect.
7.
Coolant of inferior quality.
• Replace with specified type.
8. Coolant level is low.
• Add up to specified line.
9. Water pump is faulty.
• Repair or replace.
10.
Cooling passage is clogged.
• Clean passage.
11.
Radiator is clogged.
• Clean radiator.
Low coolant level ·
Possible Cause Remedy
1. Radiator is leaky.
•
Repair or replace
2.
Hose is damaged or joint is loose.
•
Replace hose or retighten joint.
3. Water pump cover is leaky.
•
Repair or replace
4. Cylinder head gasket is fulty.
•
Replace.
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