Yamaha YFM4FAR, Service Manual

Page: 151 / 397

4 - 21
ENG
CAMSHAFT, ROCKER ARMS AND VALVES
CHECKING THE VALVES AND VALVE
SPRINGS
1.Measure:
●
Stem-to-guide clearance
Out of specification
→
Replace the valve
guide.
Stem-to-guide clearance =
valve guide inside diameter
a
–
valve stem diameter
b
Clearance (stem to guide):
Intake:
0.010 ~ 0.037 mm
(0.0004 ~ 0.0015 in)
<Limit>: 0.080 mm (0.0031 in)
Exhaust:
0.030 ~ 0.057 mm
(0.0012 ~ 0.0022 in)
<Limit>: 0.100 mm (0.0039 in)
2.Replace:
●
Valve guide
*****************************************************
Replacement steps:
NOTE:
To ease guide removal, installation and to
maintain correct fit, heat the cylinder head to
100 °C (212 °F) in an oven.
●
Remove the valve guide using a valve guide
remover
1
.
●
Install the new valve guide using a valve
guide remover
1
and valve guide installer
2
.
●
After installing the valve guide, bore the
valve guide using a valve guide reamer
3
to
obtain proper stem-to-guide clearance.
NOTE:
After replacing the valve guide reface the valve
seat.
*****************************************************
Valve guide remover (7.0 mm):
P/N. YM-01225-A, 90890-01225
Valve guide installer (7.0 mm):
P/N. YM-04017, 90890-04017
Valve guide reamer (7.0 mm):
P/N. YM-01227, 90890-01227