Valve And Valve Guide - Yamaha TTR250L Service Manual

INSPECTION AND REPAIR
NB243003

VALVE AND VALVE GUIDE

1.Measure:
Stem-to-guide clearance
Stem-to-guide clearance =
Valve guide inside diameter a –
Valve stem diameter b
Out of specification → Replace valve guide.
Stem-to-guide clearance:
Intake:
Exhaust:
2.Replace:
Valve guide
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Replacement steps:
NOTE:
Heat the cylinder head in an oven to 100 °C
(212 °F) to ease guide removal and installa-
tion and to maintain correct interference fit.
Remove the valve guide using the valve
guide remover 1.
Install the valve guide (new) using the
valve guide installer 2 and valve guide
remover 1.
After installing the valve guide, bore the
valve guide using the valve guide reamer 3
to obtain proper stem-to-guide clearance.
Valve guide remover:
5 mm (0.20 in):
Valve guide reamer:
5 mm (0.20 in):
Valve guide installer:
5 mm (0.20 in):
NOTE:
Reface the valve seat after replacing the
valve guide.
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4 - 20
ENG
0.010 ~ 0.037 mm
(0.0004 ~ 0.0015 in)
<Limit>: 0.08 mm (0.0031 in)
0.025 ~ 0.052 mm
(0.0010 ~ 0.0020 in)
<Limit>: 0.10 mm (0.0039 in)
P/N. YM-04097
P/N. YM-04099
P/N. YM-04098