Yamaha XT250X - Checking the Valve Seats

VALVES AND VALVE SPRINGS
5-20
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
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 “a”
Out of specification → Replace the valve.
6. Measure:
● Valve stem runout
Out of specification → Replace the valve.
NOTE:
●
When installing a new valve, always replace
the valve guide.
● If the valve is removed or replaced, always re-
place 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 “a”
Out of specification → Replace the cylinder
head.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Apply Mechanic’s blueing dye (Dykem) “b”
onto the valve face.
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 (ex-
haust)
0.80–1.20 mm (0.0315–0.0472 in)
Valve stem runout
Valve stem runout
0.030 mm (0.0012 in)
Limit of valve seat width (IN)
1.7 mm
Limit of valve seat width (EX)
1.7 mm