User Manual - Page 88

For CRF450R.

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Servicing Your Honda 83
Valve Clearance
6. Lift the rocker arms (12) up and remove the
shims (13).
Be careful not to damage the intake rocker arms.
Do not clean the intake rocker arms using a
commercially available compound cleaner.
1. Measure the shim thickness with a micrometer
and record it.
Seventy-three different shims (1) are available
in 0.025 mm thickness intervals, from 1.200
mm (the thinnest) to 3.000 mm (the thickest).
2. Calculate the new shim thickness using the
equation below.
A = (B – C) + D
A: New shim thickness
B: Recorded valve clearance
C: Specified valve clearance
D: Old shim thickness
Make sure of the correct shim thickness by
measuring the shim with a micrometer.
Reface the exhaust valve seat if carbon deposits
result in a calculated dimension of over 3.000
mm.
Do not lap the intake valves. They are titanium and
have a thin oxide coating. Lapping will damage
this coating.
If a calculated dimension is out of specifications,
have your motorcycle inspected by your dealer.
(12) rocker arms
(13) shims
(13)
(12)
(13)
(12)
Shim Selection
(1) shim
(1)
1.80 mm 1.825 mm 1.85 mm
1.875 mm
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