Honda CRF450R Owner's Manual page 39

Measure the intake valve clearance and exhaust valve
clearance.
VALVE CLEARANCES:
IN: 0.006 0.001 in (0.16 0.03 mm)
EX: 0.011 0.001 in (0.28 0.03 mm)
(1) FEELER GAUGE
Install the new sealing washer and cam chain tensioner
lifter cover bolt.
(1) SEALING WASHER
(2) CAM CHAIN TENSIONER LIFTER COVER BOLT
Measure the decompressor arm clearance by inserting
a feeler gauge between the decompressor arm adjust-
ing screw and right side rocker arm.
DECOMPRESSOR CLEARANCE:
RIGHT EXHAUST VALVE CLEARANCE
0.014 in (0.35 mm)
ex)
If measured right exhaust valve clearance is 0.011 in
(0.28 mm), decompressor clearance is;
0.011 in (0.28 mm) + 0.014 in (0.35 mm) = 0.025 in (0.63 mm)
(1) FEELER GAUGE
(2) DECOMPRESSOR ARM ADJUSTING SCREW
(3) EXHAUST ROCKER ARM
(4) RIGHT EXHAUST VALVE
If decompressor arm clearance needs adjustment, see
Decompressor Arm Clearance Adjustment (this page).
Decompressor Arm Clearance Adjustment
Make sure that the piston is at top dead center on the
compression stroke (page 30).
Measure the right exhaust valve clearance by inserting
a feeler gauge between the right side rocker arm and
shim.
VALVE CLEARANCE:
EX: 0.011 0.001 in (0.28 0.03 mm)
(1) FEELER GAUGE
(2) EXHAUST ROCKER ARM
(3) SHIM
Pull out the feeler gauge between the right side rocker
arm and shim.
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