Yamaha 2009 YFM25RY, Service Manual, Page: 184 / 293

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)