Sym PA12B Service Manual page 106

Valve Stem Inspection
Check if valve stem is bent, cracked or burnt.
Check the operation condition of valve stem in
valve guide, and measure the valve stem
outer diameter.
Service Limit:
Intake valve: Under 5.42mm
Exhaust valve: Under 5.40mm
Valve Guide Inspection
Caution
Clear all the carbon deposit with reamer
before measuring the valve guides
Special tool: Valve Guide Reamer 5.0mm
Measure and record each valve guide inner
diameters.
Service Limit：5.50mm
The difference that the inner diameter of valve
guide deducts the outer diameter of valve
stem is the clearance value between the valve
stem and valve guide.
Service Limit：
Intake: Over 0.08mm
Exhaust: Over 0.10mm
Caution
If clearance is over service limit, check if
only replaces new valve guide will fix the
clearance into service limit or not. If yes,
replace valve guide only.
Fix the guides with reamer after replacement.
If clearance still exceeds service limit after
replacing valve guides, please also replace
valve stem too.
Caution
Fix the valve seat when replacing valve
guides.
To this chapter contents
Valve Guide Reamer 5.0mm
.
Valve Guide Reamer 5.0mm
7. Cylinder Head / Valve
7-9