Sym Citycom.300i, Service Manual

Page: 120 / 270

6
. Cylinder Head / Valve
6-3
Troubleshooting
Engine performance will be affected by troubles on engine top parts. The trouble usually can be
determined or by performing cylinder compression test and judging the abnormal noise generated.
Low compression pressure
1. Valve

Improper valve adjustment

Burnt or bent valve

Improper valve timing
 Valve spring damage

Valve carbon deposit.
2. Cylinder head

Cylinder head gasket leaking or damage

Tilt or crack cylinder
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

Chain wear out or looseness

Auto-tensioner wear out or damage
 Camshaft sprocket
 Rocker arm or rocker arm shaft wear out
To this chapter contents