Yamaha GRIZZLY Ultramatic YFM660FP, Service Manual

Page: 171 / 408

4 - 28
ENG
VALVES AND VALVE SPRINGS
8.Measure:
●
Valve seat width
a
Out of specification
→
Reface the valve seat.
*****************************************************
Measurement steps:
●
Apply Mechanic’s blueing dye (Dykem)
b
to
the valve face.
●
Install the valve into the cylinder head.
●
Press the valve through the valve guide and
onto the valve seat to make a clear pattern.
●
Measure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.
●
If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat must
be refaced.
*****************************************************
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)
9.Lap:
●
Valve face
●
Valve seat
NOTE:
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
*****************************************************
Lapping steps:
●
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.
●
Apply molybdenum disulfide oil to the valve
stem.