Checking The Valves And Valve Guides - Yamaha WR450F Owner's Service Manual

4. Remove:
• Valve spring retainer "1"
• Valve spring "2"
• Valve "3"
• Valve stem seal "4"
• Valve spring seat "5"
TIP
Identify the position of each part very carefully
so that it can be reinstalled in its original place.
2
4
5
CHECKING THE VALVES AND VALVE
EAS2GC1251
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)
0.020–0.047 mm (0.0008–0.0019
in)
Limit
0.100 mm (0.0039 in)
1
3
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".
1
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
15.1–15.5 mm (0.59–0.61 in)
Exhaust
12.2–12.6 mm (0.48–0.50 in)
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