Troubleshooting - Sym PA12B Service Manual

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
Improper valve clearance adjustment
Burnt or bent valve
Improper valve timing
Valve spring damage
Valve carbon deposit.
Valve seat warpage
Spark plug not tightened of badly assembled.
2. Cylinder head
Cylinder head gasket leaking or damage
Tilt or crack cylinder
3. Piston
Piston rings worn out.
High compression pressure
Too much carbon deposit on combustion chamber or piston head
Abnormal noise
Improper valve clearance adjustment
Burnt valve or damaged valve spring
Camshaft wear out or damage
Chain wear out or looseness
Auto-tensioner wear out or damage
Camshaft sprocket
Rocker arm or rocker arm shaft wear out
Smoke from exhaust pipe:
Valve guide or stem worn
Valve guide oil seal worn
To this chapter contents
7. Cylinder Head / Valve
7-3