Yamaha YFM25RY Automobile User Manual


 
VALVES AND VALVE SPRINGS
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3. Eliminate:
Carbon deposits
(from the valve face and valve seat)
4. Check:
•Valve face
Pitting/wear Grind the valve face.
Valve stem end
Mushroom shape or diameter larger than
the body of the valve stem Replace the
valve.
5. Measure:
Valve margin thickness D “a”
Out of specification Replace the valve.
6. Measure:
Valve stem runout
Out of specification Replace the valve.
TIP
When installing a new valve, always replace
the valve guide.
If the valve is removed or replaced, always
replace the oil seal.
EAS24300
CHECKING THE VALVE SEATS
The following procedure applies to all of the
valves and valve seats.
1. Eliminate:
Carbon deposits
(from the valve face and valve seat)
2. Check:
Valve seat
Pitting/wear Replace the cylinder
head.
3. Measure:
Valve seat width C “a”
Out of specification Replace the cylin-
der head.
Valve guide remover (ø6)
90890-04064
Valve guide remover (6.0 mm)
YM-04064-A
Valve guide installer (ø6)
90890-04065
Valve guide installer (6.0 mm)
YM-04065-A
Valve guide reamer (ø6)
90890-04066
Valve guide reamer (6.0 mm)
YM-04066
Valve margin thickness
Valve margin thickness D
(intake)
0.80–1.20 mm (0.0315–0.0472
in)
Valve margin thickness D
(exhaust)
0.80–1.20 mm (0.0315–0.0472
in)
Valve stem runout
0.01 mm (0.0004 in)
Valve seat width
Valve seat width C (intake)
0.90–1.10 mm (0.0354–0.0433
in)
Valve seat width C (exhaust)
0.90–1.10 mm (0.0354–0.0433
in)