Honda CRF450RX 2020 Owner's Manual & Competition Handbook page 88

6. Lift the rocker arms (12) up and remove the
shims (13).
(12)
(13)
(12) rocker arms
(13) shims
Be careful not to damage the intake rocker arms.
Do not clean the intake rocker arms using a
commercially available compound cleaner.
Shim Selection
(13)
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).
(12)
(1) shim
2. Calculate the new shim thickness using the
A = (B – C) + D
A: New shim thickness
B : Recorded valve clearance
C : Specified valve clearance
D: Old shim thickness
(1)
• 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.
1.80 mm
Valve Clearance
equation below.
1.825 mm 1.85 mm
Servicing Your Honda
1.875 mm
83