Checking The Valve Seats - Yamaha WR450FB 2012 Owner's Service Manual

TIP
After replacing the valve guide, reface the valve
seat.
Intake
Valve guide remover (ø4.5)
90890-04116
YM-04116
Valve guide installer (ø4.5)
90890-04117
YM-04117
Valve guide reamer (ø4.5)
90890-04118
YM-04118
Exhaust
Valve guide remover(ø5.0)
90890-04097
YM-04097
Valve guide installer (ø5.0)
90890-04098
YM-04098
Valve guide reamer (ø5.0)
90890-04099
YM-04099
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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
valve.
5. Measure:
• Valve margin thickness "a"
Out of specification
Valve margin thickness D (intake)
1.00 mm (0.0394 in)
Valve margin thickness D (ex-
haust)
1.00 mm (0.0394 in)
Replace the
Replace the valve.
6-21
VALVES AND VALVE SPRINGS
6. Measure:
• Valve stem runout
Out of specification
TIP
• When installing a new valve, always replace
the valve guide.
• If the valve is removed or replaced, always re-
place the oil seal.
Valve stem runout
0.010 mm (0.0004 in)
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 "a"
Out of specification
head.
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)
Replace the valve.
Replace the cylinder