Cylinder Head Inspection - Sym Fiddle II 50 Series Service Manual

6. CYLINDER HEAD/VALVE

CYLINDER HEAD INSPECTION

Check if spark plug and valve holes are crack.
Measure cylinder head flat with a
straightedge and flat feeler gauge.
Service limit: below 0.05mm
Valve spring free length
Measure the free length of intake and
exhaust valve springs.
Standard:
35.250 mm
Valve stem
Check if valve stems are bend, crack or burn.
Check the operation condition of valve stem
in valve guide, and measure & record the
valve stem outer diameter.
Service Limit: IN¡ ÷
EX¡ ÷
Valve guide
Caution
Before measuring the valve guide, clean
carbon deposits with reamer.
Special Service Tool: 5.0mm valve guide
reamer
Measure and record each valve guide inner
diameters.
Service limit: 5.030mm
The difference that the inner diameter of
valve guide deducts the outer diameter of
valve stem is the clearance between the
valve stem and valve guide.
Service Limit: IN¡ ÷
EX¡ ÷
6-8
4.900mm
4.900mm
0.08mm
0.10mm
The narrow pitch of the spring shall face to the
combustion chamber.
5.0mm valve guide reamer
SYM