Yamaha XVS6501997, Service Manual

Page: 128 / 327

4-24
b
VALVES AND VALVE SPRINGS
ENG
NOTE:
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5. Measure:
S
Runout (valve stem)
Out of specification
Replace.
Runout limit:
0.03 mm
D
When installing a new valve always replace
the guide.
D
If the valve is removed or replaced always re-
place the oil seal.
6. Eliminate:
S
Carbon deposits
(from the valve face and valve seat)
7. Inspect:
S
Valve seats
Pitting/ wear
Reface the valve seat.
8. Measure:
S
Valve seat width a
Out of specification Reface the valve
seat.
Valve seat width:
Intake:
1.0 1.2 mm
<Limit>: 1.8 mm
Exhaust:
1.0 1.2 mm
<Limit>: 1.8 mm
Measurement steps:
D
Apply Mechanic’s blueing dye (Dykem) b to
the valve face.
D
Install the valve into the cylinder head.
D
Press the valve through the valve guide and
onto the valve seat to make a clear pattern.
D
Measure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.
D
If the valve seat is too wide, too narrow, or the
seat is not centered, the valve seat must be
refaced.