Sym ALA125CC Manual page 142

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: 0.5mm
Valve spring free length
Measure the free length of intake and
exhaust valve springs.
Standard
Outer : 35.250 mm
Inner : 32.410 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→ 4.900mm
EX→ 4.900mm
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→ 0.08mm
EX→ 0.10mm
6-8
The narrow pitch of the spring shall face to the
combustion chamber.
5.0mm valve guide reamer
SYM