Sym PA12B - Troubleshooting

7. Cylinder Head / Valve
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Troubleshooting
Engine performance will be affected by troubles on cylinder-head perimeter parts. The trouble
usually can be determined or by performing cylinder compression test or judging the abnormal
noise.
Poor Idling
Compression pressure is too low.
Low compression pressure
1. Valve
y Improper valve clearance adjustment
y Burnt or bent valve
y Improper valve timing
y Valve spring damage
y Valve carbon deposit.
y Valve seat warpage
y Spark plug not tightened of badly assembled.
2. Cylinder head
y Cylinder head gasket leaking or damage
y Tilt or crack cylinder
3. Piston
y Piston rings worn out.
High compression pressure
y Too much carbon deposit on combustion chamber or piston head
Abnormal noise
y Improper valve clearance adjustment
y Burnt valve or damaged valve spring
y Camshaft wear out or damage
y Chain wear out or looseness
y Auto-tensioner wear out or damage
y Camshaft sprocket
y Rocker arm or rocker arm shaft wear out
Smoke from exhaust pipe:
z Valve guide or stem worn
z Valve guide oil seal worn
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