Yamaha YZ450FT Owner's Service Manual page 144

VALVES AND VALVE SPRINGS
NOTE:
After replacing the valve guide reface the
valve seat.
3. Inspect:
• Valve face
• Valve stem end
4. Measure:
• Margin thickness a
4 - 36
ENG
Valve guide remover:
Intake: 4.5 mm (0.18 in)
YM-4116/90890-04116
Exhaust: 5.0 mm (0.20 in)
YM-4097/90890-04097
Valve guide installer:
Intake:
YM-4117/90890-04117
Exhaust:
YM-4098/90890-04098
Valve guide reamer:
Intake: 4.5 mm (0.18 in)
YM-4118/90890-04118
Exhaust: 5.0 mm (0.20 in)
YM-4099/90890-04099
Pitting/wear → Grind the face.
Mushroom shape or diameter larger than
the body of the stem → Replace.
Out of specification → Replace.
Margin thickness:
Intake:
1.0 mm (0.039 in)
<Limit>: 0.85 mm (0.033 in)
Exhaust:
1.0 mm (0.039 in)
<Limit>: 0.85 mm (0.033 in)