Cylinder Head/Valve Troubleshooting - Honda TRX450R Service Manual

CYLINDER HEAD/VALVE
TROUBLESHOOTING
• Engine top-end problems usually affect engine performance. These problems can be diagnosed by a compression test,
or by tracing top-end noise with a sounding rod or stethoscope.
• If the performance is poor at low speeds, check for white smoke in the crankcase breather hose. If the hose is smoky,
check for a seized piston ring (page 12-7).
Compression too low, hard starting or poor performance at low speed
• Valves
- Incorrect valve adjustment
- Burned or bent valve
- Incorrect valve timing
- Weak valve spring
- Uneven valve seating
- Valve stuck open
• Cylinder head
- Leaking or damaged cylinder head gasket
- Warped or cracked cylinder head
- Loose spark plug
• Cylinder/piston problem (page 12-4).
Compression too high
• Excessive carbon build-up on piston head or combustion chamber
• Worn or damaged decompressor system
Excessive smoke
• Worn valve stem or valve guide
• Damaged stem seal
• Cylinder/piston problem (page 12-4).
Excessive noise
• Incorrect valve adjustment
• Sticking valve or broken valve spring
• Excessive worn valve seat
• Worn or damaged camshaft
• Worn rocker arm and/or shaft
• Worn rocker arm follower and valve stem end
• Worn or damaged valve lifter
• Worn cam sprocket teeth
• Worn cam chain
• Worn or damaged cam chain tensioner
• Cylinder/piston problem (page 12-4).
Rough idle
• Low cylinder compression
11-7