Checking The Valve Seats - Yamaha XG250 Service Manual

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
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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.
Valve margin thickness
Valve margin thickness D (intake)
0.80–1.20 mm (0.0315–0.0472 in)
Valve margin thickness D (ex-
haust)
0.80–1.20 mm (0.0315–0.0472 in)
6. Measure:
Valve stem runout
●
Out of specification → Replace the valve.
NOTE:
When installing a new valve, always replace
●
the valve guide.
VALVES AND VALVE SPRINGS
●
EAS24300

CHECKING THE VALVE SEATS

The following procedure applies to all of the
valves and valve seats.
1. Eliminate:
●
2. Check:
●
3. Measure:
●
a
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a. Apply Mechanic's blueing dye (Dykem) "b"
5-20
If the valve is removed or replaced, always re-
place the oil seal.
Valve stem runout
Valve stem runout
0.030 mm (0.0012 in)
Carbon deposits
(from the valve face and valve seat)
Valve seat
Pitting/wear → Replace the cylinder head.
Valve seat width "a"
Out of specification → Replace the cylinder
head.
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)
a
onto the valve face.