Yamaha YZ450F Owner's Service Manual page 102

3. Remove:
• Timing mark accessing screw "1"
• Crankshaft end accessing screw "2"
• O-ring
1
4. Check:
• Valve clearance
Out of specification  Regulate.
Valve clearance (cold)
Intake
0.13–0.20 mm (0.0051–0.0079 in)
Exhaust
0.18–0.25 mm (0.0071–0.0098 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.
d
c. Measure the valve clearance "e" using a
thickness gauge "1".
2
TIP
Record the measured reading if the clearance
is incorrect.
b
a
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5. Adjust:
• Valve clearance
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a. Remove the camshaft (intake and exhaust).
Refer to "CAMSHAFT" on page 5-12.
b. Remove the valve lifter "2" and the adjusting
pad "3" with a valve lapper "1".
TIP
• Place a cloth in the timing chain space to pre-
vent adjusting pads from falling into the crank-
case.
• Identity each valve lifter and adjusting pad po-
sition very carefully so that they can be rein-
stalled in their original place.
3-18
e
1
ENGINE
c
e