Cylinder Head/Valves Troubleshooting - Honda PCX150 2013 Service Manual

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CYLINDER HEADNALVES
• Engine top-end problems usually affect engine performance. These can be diagnosed by a compression test or by tracing
engine noises to the top-end 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 11-8).
Compression too low, hard starting or poor performance at low speed
Valves:
- Incorrect valve adjustment
- Burned or bent valve
- Incorrect valve timing
- Broken valve spring
- Uneven valve seating
- Valve stuck open
- Weak valve spring
Cylinder head:
- Leaking or damaged cylinder head gasket
- Warped or cracked cylinder head
- Loose spark plug
Worn cylinder (page 11-5).
Worn piston or piston rings (page 11-8).
Compression too high, overheating or knocking
• Excessive carbon build-up on piston head or on combustion chamber
Excessive smoke
• Worn valve stem or valve guide
• Damaged stem seal
Worn cylinder (page 11-5) .
• Worn piston or piston rings (page 11-8).
Excessive noise
• Incorrect valve adjustment
• Sticking valve or broken valve stem
Excessively worn valve seat
• Worn or damaged camshaft
• Worn or damaged cam chain
• Worn cam sprocket teeth
• Worn rocker arm and/or shaft
• Worn or damaged cam chain tensioner
• Worn cylinder (page 11-5).
• Worn piston or piston rings (page 11-8).
Rough idle
• Low cylinder compression
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