Yamaha 5KM2-AE1 Service Manual page 174

VALVES AND VALVE SPRINGS
8.Measure:
Valve seat width a
G
Out of specification → Reface the valve seat.
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Measurement steps:
Apply Mechanic's blueing dye (Dykem) b to
G
the valve face.
G
Install the valve into the cylinder head.
G
Press the valve through the valve guide and
onto the valve seat to make a clear pattern.
G
Measure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.
G
If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat must
be refaced.
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9.Lap:
Valve face
G
Valve seat
G
NOTE:
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
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Lapping steps:
G
Apply a coarse lapping compound to the
valve face.
CAUTION:
Do not let the compound enter the gap
between the valve stem and the guide.
G
Apply molybdenum disulfide oil to the valve
stem.
4 - 28
ENG
Valve seat width:
Intake:
0.9 ~ 1.1 mm
(0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)
Exhaust:
0.9 ~ 1.1 mm
(0.0354 ~ 0.0433 in)
<Limit>: 1.6 mm (0.0630 in)