Yamaha XG250 Service Manual page 161

Valve-stem-to-valve-guide clearance =
Valve guide inside diameter "a" -
Valve stem diameter "b"
Valve-stem-to-valve-guide
ance
Valve-stem-to-valve-guide
ance (intake)
0.010–0.037 mm (0.0004–0.0015
in)
Limit
0.080 mm (0.0032 in)
Valve-stem-to-valve-guide
ance (exhaust)
0.025–0.052 mm (0.0010–0.0020
in)
Limit
0.100 mm (0.0039 in)
a
b
2. Replace:
Valve guide
●
NOTE:
To ease valve guide removal and installation,
and to maintain the correct fit, heat the cylinder
head to 100°C (212°F) in an oven.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Remove the valve guide with the valve guide
remover "1".
VALVES AND VALVE SPRINGS
clear-
clear-
b. Install the new valve guide with the valve
guide installer "2" and valve guide remover
"1".
clear-
c. After installing the valve guide, bore the valve
guide with the valve guide reamer "3" to ob-
tain the proper valve-stem-to-valve-guide
clearance.
NOTE:
After replacing the valve guide, reface the valve
seat.
5-19
1
2
3