Yamaha Scorpio, Service Manual

Page: 103 / 300

4 - 26
ENG
VALVES AND VALVE SPRINGS
3.Measure:
●
Valve seat width
a
Out of specification
→
Reface the valve seat.
***********************************************
Measurement steps:
●
Apply Mechanic’s blueing dye (Dykem)
1
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 replaced.
***********************************************
Valve seat width:
Intake:
0.9 ~ 1.1 mm
<Limit: 1.6 mm>
Exhaust:
0.9 ~ 1.1 mm
<Limit: 1.6 mm>
EB402020
4.Lap:
●
Valve face
●
Valve seat
NOTE:
After replacing the valve seat, valve and valve
guide, the valve seat and valve face should be
lapped.
***********************************************
Lapping steps:
●
Apply a coarse lapping compound
a
to the
valve face.
CAUTION:
Do not let compound enter the gap
between the valve stem and the guide.
●
Apply molybdenum disulfide oil to the valve
stem.