Yamaha YFM90RA Model Vehicle User Manual


 
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ENG
CAMSHAFT, ROCKER ARMS AND VALVES
2. Check:
valve face
Pitting/wear Grind the face.
valve stem end
Mushroom shape or diameter larger than
the body of the stem Replace.
3. Measure:
margin thickness
Out of specification Replace.
Margin thickness
Intake
0.5 ~ 0.9 mm
(0.0197 ~ 0.0354 in)
Exhaust
0.6 ~ 1.0 mm
(0.0236 ~ 0.0394 in)
4. Measure:
runout (valve stem)
Out of specification Replace.
TIP
When installing a new valve always replace
the guide.
If the valve is removed or replaced always
replace the oil seal.
5. Eliminate:
carbon deposits
(from the valve face and valve seat)
6. Check:
valve seats
Pitting/wear Reface the valve seat.
Runout limit
0.02 mm (0.0008 in)
a