Yamaha F4 Service Manual page 156

POWR
a
d
ROCKER ARM AND VALVES
b
c
SERVICE POINTS
Valve inspection
1. Measure:
Valve guide inside diameter a
9
Out of specification ® Replace the
valve guide.
Valve guide inside diameter:
5.500 ~5.512 mm
(0.216 ~ 0.217 in)
2. Measure:
Valve seat width b
9
Out of specification ® Reface the
valve seat.
Valve seat width :
Intake :
0.6 ~ 0.8 mm (0.02 ~ 0.03 in)
Exhaust :
0.6 ~ 0.8 mm (0.02 ~ 0.03 in)
3. Measure:
Margin thickness c
9
Out of specification ® Replace the
valve.
Margin thickness:
Intake : 0.70 mm (0.028 in)
Exhaust : 1.00 mm (0.039 in)
4. Measure:
Valve stem diameter d
9
Out of specification ® Replace the
valve.
Diameter:
IN :5.475 ~ 5.490 mm
(0.2156 ~ 0.2161 in)
EX:5.460 ~ 5.475 mm
(0.2150 ~ 0.2156 in)
5-16
E