Cylinder Head/Valve Troubleshooting - Honda TRX500FM Service Manual

CYLINDER HEADNALVE
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 a white smoke in the crankcase breather hose. If the hose is smoky, check
for seized piston ring (page 11-2).
Compression too low, hard starting or poor performance at low speed
Valves
- Incorrect valve adjustment
- Burned or bent valves
- Incorrect valve timing
- Broken valve spring
- Uneven valve seating
- Valve stuck open
Cylinder head
- leaking or damaged cylmder head gasket
- Warped or cracked cylinder head
- loose spark plug
Cylinder/piston problem (page 11-3)
Compression too high
• Excessive carbon build-up on piston head or combustion chamber
• Worn or damaged decompressor system
E}l:cessive smoke
Worn valve stem or valve guide
• Damaged stem seal
• Cylinder/piston problem (page 11-3)
Excessive noise
Incorrect valve dearance
Sticking ",al",e or broken valve spring
Excessively worn valve seat
Worn or damaged camshaft
Worn rocker arm
andlor
shaft
Worn rocker arm follower or valve stem end
Worn or damaged push rod and/or cam follower
Worn cam chain
Worn or damaged cam chain tensioner
Worn cam sprocketleeth
Cylinder/piston problem (page 11-3)
Rough idle
• Low cylinder compression
10-6