Troubleshooting - KYMCO VENOX 250 Service Manual

6. CYLINDER HEAD/VALVES

TROUBLESHOOTING

• The poor cylinder head operation can be diagnosed by a compression test or by tracing engine
top-end noises.
Poor performance at idle speed
• Compression too low
Compression too low
• Incorrect valve clearance (too small)
• Burned or bend valves
• Incorrect valve timing
• Broken valve spring
• Poor valve and seat contact
• Leaking cylinder head gasket
• Warped or cracked cylinder head
• Poorly installed spark plug
Compression too high
• Excessive carbon build-up in combustion
chamber or on piston head
6-3
White smoke from exhaust muffler
• Worn or broken valve stem or valve guide
• Damaged valve stem seal
Abnormal noise
• Incorrect valve clearance (too large)
• Burned valve or rocker arm
• Worn camshaft or cam follower
VENOX 250