Yamaha YZ250F(R) Owner's Service Manual page 324

VALVES AND VALVE SPRINGS
NOTE:
After replacing the valve guide reface the
valve seat.
3. Inspect:
4. Measure:
4 - 36
Valve guide remover:
Intake: 4.0 mm (0.16 in)
YM-4111/90890-04111
Exhaust: 4.5 mm (0.18 in)
YM-4116/90890-04116
Valve guide installer:
Intake: 4.0 mm (0.16 in)
YM-4112/90890-04112
Exhaust: 4.5 mm (0.18 in)
YM-4117/90890-04117
Valve guide reamer:
Intake: 4.0 mm (0.16 in)
YM-4113/90890-04113
Exhaust: 4.5 mm (0.18 in)
YM-4118/90890-04118
Valve face
G
Pitting/wear → Grind the face.
Valve stem end
G
Mushroom shape or diameter larger
than the body of the stem → Replace.
Margin thickness a
G
Out of specification → Replace.
Margin thickness:
Intake:
0.8 mm (0.0315 in)
Exhaust:
0.7 mm (0.0276 in)
ENG