Yamaha TT-R125EY Service Manual page 119

VALVES AND VALVE SPRINGS
INSPECTION
Valve
1. Measure:
2. Replace:
To ease guide removal, installation and to
maintain correct fit heat the cylinder head in
an over to 100 °C (212 °F).
TIP
After replacing the valve guide reface the valve
seat.
4-26
• Stem-to-guide clearance
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 (0.0031 in)
Exhaust:
0.025 ~ 0.052 mm
(0.0010 ~ 0.0020 in)
<Limit>: 0.10 mm (0.0040 in)
• Valve guide
Replacement steps:
TIP
• Remove the valve guide using a valve guide
remover 1.
• Install the new valve guide using a valve
guide remover and valve guide installer.
• After installing the valve guide, bore the valve
guide using a valve guide reamer 2 to obtain
proper stem-to-guide clearance.
Valve guide remover:
YM-4097/90890-04097
Valve guide installer:
YM-4098/90890-04098
Valve guide reamer:
YM-04099/90890-04099
ENG