Honda CRF250X 2007 Owner's Manual & Competition Handbook page 75

Valve Clearance
Shim Selection
1. Clean the valve shim contact area in the valve
lifter (1) with compressed air.
(1) valve lifter
70
Servicing Your Honda
2. Measure the shim thickness with a micrometer
and record it.
Sixty-nine different thickness shims (2) are
available from the thinnest (1.200 mm
thickness) shim to the thickest (2.900 mm
thickness) in intervals of 0.025 mm.
(1)
(2) shim
3. 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
(2)
• Make sure of the correct shim thickness by
measuring the shim with a micrometer.
• Reface the intake valve seat if carbon deposits
result in a calculated dimension of over 2.450
mm.
Reface the exhaust valve seat if carbon
deposits result in a calculated dimension of
over 2.900 mm.