Cylinder Head/Valve Troubleshooting; Low Compression Pressure; High Compression Pressure; White Smoke - SANYANG INDUSTRY CO. SYM Service Manual

SYM
TROUBLE SHOOTING
Engine performance will be effected by troubles on engine top end. The troubles usually can
be determinate or by performing cylinder compression test and judging the abnormal noise
generated.
Rough Idle

Low compression pressure.

Low compression pressure
1. Valve
Improper valve adjustment.
Burnt or bended valve.
Improper valve timing.
Valve spring damaged.
Valve carbon.
Poor sealing on valve seat.
Improper spark plug installation.
2. Cylinder head
Cylinder head gasket leaking or damage.
Tilt or crack cylinder surface.
3. Piston
Piston ring worn out.

High compression pressure

Too much carbon deposit on combustion chamber or piston head.
Noise
Improper valve clearance adjustment
Burnt valve or damaged valve spring
Camshaft wear out or damage
Cam chain wear out or looseness
Auto-adjuster wear out or damage of cam chain
Camshaft sprocket wear out
Rocker arm or rocker arm shaft wear out

White smoke

Valve guide or valve stem wear out
Valve stem seal wear out
6. CYLINDER HEAD/VALVE
6-3