Yamaha YZ450F 2006, Owner'S Service Manual, Page: 312 / 650

4 - 36
ENG
VALVES AND VALVE SPRINGS
INSPECTION
Valve
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>: 0.08 mm (0.003 in)
Exhaust:
0.020 ~ 0.047 mm
(0.0008 ~ 0.0019 in)
<Limit>: 0.10 mm (0.004 in)
2. Replace:
• Valve guide
Replacement steps:
NOTE:
To ease guide removal, installation and to
maintain correct fit heat the cylinder head in
an over to 100 °C (212 °F).
• 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.