Yamaha WR250F 2017 Owner's Service Manual page 120

2. Remove:
• Spark plug
• Cylinder head cover
Refer to "CAMSHAFT" on page 6-12.
3. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw "2"
• O-ring
4. Check:
• Valve clearance
Out of specification  Regulate.
Valve clearance (cold)
Intake
0.12–0.19 mm (0.0047–0.0075 in)
Exhaust
0.17–0.24 mm (0.0067–0.0094 in)
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a. Turn the crankshaft counterclockwise with a
wrench.
b. Align the top dead center (TDC) mark "a" on
the rotor with the alignment mark "b" on the
crankcase cover.
TIP
Check that the alignment mark "c" on the cam-
shaft sprocket and the alignment mark "d" on
the intake camshaft sprocket are aligned with
the edge of the cylinder head.
1
2
b
a
3-20
d
c. Measure the valve clearance "e" using a
thickness gauge "1".
TIP
Record the measured reading if the clearance
is incorrect.
e
1
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5. Adjust:
• Valve clearance
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a. Remove the camshaft (intake and exhaust).
Refer to "CAMSHAFT" on page 6-12.
b. Remove the valve lifter "2" and the adjusting
pad "3" with a valve lapper "1".
ENGINE
c
e