Yamaha WR250F Manuel D'atelier page 338

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VALVES AND VALVE SPRINGS
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
NOTE:
After replacing the valve guide reface the
valve seat.
3. Inspect:
Valve face
Pitting/wear → Grind the face.
Valve stem end
Mushroom shape or diameter larger
than the body of the stem → Replace.
4. Measure:
Margin thickness a
Out of specification → Replace.
Margin thickness:
Intake:
0.8 mm (0.0315 in)
Exhaust:
0.7 mm (0.0276 in)
ENG