Yamaha YZ450F Manuel D'atelier Du Proprietaire page 308

VALVES AND VALVE SPRINGS
INSPECTION
Valve
1. Measure:
2. Replace:
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).
G
G
G
4 - 35
Stem-to-guide clearance
G
Stem-to-guide clearance =
valve guide inside diameter a –
valve stem diameter b
Out of specification → Replace the
valve guide.
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)
Valve guide
G
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.
ENG