Checking The Valves And Valve Guides - Yamaha YZ250F Owner's Service Manual

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CHECKING THE VALVES AND VALVE
EAS1SM5222
GUIDES
1. Measure:
• Valve-stem-to-valve-guide clearance
Out of specification  Replace the valve
guide.
Valve-stem-to-valve-guide clearance =
Valve guide inside diameter "a" -
Valve stem diameter "b"
Valve-stem-to-valve-guide clear-
ance (intake)
0.010–0.037 mm (0.0004–0.0015
in)
Limit
0.080 mm (0.0032 in)
Valve-stem-to-valve-guide clear-
ance (exhaust)
0.025–0.052 mm (0.0010–0.0020
in)
Limit
0.100 mm (0.0039 in)
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VALVES AND VALVE SPRINGS
2. Replace:
• Valve guide
TIP
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.
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a. Remove the valve guide with the valve guide
remover "1".
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b. Install the new valve guide with the valve
guide installer "2" and the valve guide re-
mover "1".
Valve guide installation height "a"
Intake
10.8–11.2 mm (0.43–0.44 in)
Exhaust
11.2–11.6 mm (0.44–0.46 in)
c. After installing the valve guide, expand the
hole in the valve guide with the valve guide
reamer "3" to obtain the proper valve-stem-
to-valve-guide clearance.
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