Checking The Valve Seats - Yamaha XT250X 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
G
(from the valve face and valve seat)
4. Check:
Valve face
G
Pitting/wear → Grind the valve face.
Valve stem end
G
Mushroom shape or diameter larger than the
body of the valve stem → Replace the valve.
5. Measure:
Valve margin thickness "a"
G
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
G
Out of specification → Replace the valve.
NOTE:
When installing a new valve, always replace
G
the valve guide.
If the valve is removed or replaced, always re-
G
place the oil seal.
VALVES AND VALVE SPRINGS
Valve stem runout
Valve stem runout
0.030 mm (0.0012 in)
EAS24300

CHECKING THE VALVE SEATS

The following procedure applies to all of the
valves and valve seats.
1. Eliminate:
Carbon deposits
G
(from the valve face and valve seat)
2. Check:
Valve seat
G
Pitting/wear → Replace the cylinder head.
3. Measure:
Valve seat width "a"
G
Out of specification → Replace the cylinder
head.
Limit of valve seat width (IN)
1.7 mm
Limit of valve seat width (EX)
1.7 mm
MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM
a. Apply Mechanic's blueing dye (Dykem) "b"
onto the valve face.
5-20