Honda CRF450R 2009 Service Manual page 265

CYLINDER HEADNALVES
VALVENALVE GUIDE
Inspect each valve for out-of-round, burns, scratches or , - -- - - - - - - - - - - - - - - - - ,
Taka cere nol /0 till
or
lean the reamer
in the guide while
reaming.
abnormal stem wear.
Check Ihe valve movement in the guide.
Measure and record Ihe valve stem 0.0.
STANDARD:
IN : 4 .975 - 4 .990 mm (0.1959 - 0.1965 in)
EX: 4.965 - 4 .980 mm (0.1955 - 0.1961 in)
SERVICE LIMIT :
EX: 4 .96 mm (0.195 in)
Ream the valve guide to remove any carbon build-up
before measuring the guide 1 .0.
Insert the reamer from the combustion chamber side of
the cylinder head and always rolate the reamer
clockwise.
TOOL:
Valve guide reamer, 5.0 mm 07984·MA60001 or
07984·MA60000
(U.S.A. only)
Measure and record each valve guide 1.0. in the
combustion chamber.
SERVICE LIMIT: 5.052 mm (0.1989 in)
Subtract each valve stem 0.0. from the corresponding
guide 1.0.
10
obtain the slem·to-guide clearance.
STANDARD:
IN: 0.010 - 0.037 mm (0.0004 - 0.0015 in)
EX : 0.020 - 0.047 mm (O.OOOS - 0.0019 i n)
RefBCB the valve
If the stem.lo..guide clearance exceeds the service
se<Jls whenever Ihe
limils, determine if a new guide with standard
valwJ guides are
dimensions would bring the clearance within tolerance.
rep/aced
If so, replace the guides as necessary and ream 10 fit.
(page g·24).
If the slem-to-guide clearance e)(ceeds Ihe service
limits with new guides also. replace the valves and
guides .
VALVE GUIDE REPLACEMENT
Be sure
10
wear
heavy gloves when
handling !he heated
cylinder head.
Using
a
lorch
10
heat lhe cylinder
head may cause
warpage.
Mark new valve guides at the proper depth (see
specification page 9-24) using a marker. Chill a new
valve guides in a freezer for about
1
hour.
Heat the cylinder head to 100 -
150 ~C
(212 - 302°F)
with a hot plate or oven. Do not heat the cylinder head
beyond 1S0· C (320QF). Use tempera ture indicator
sticks, available from welding supply stores, 10 be sure
the cylinder head is heated to the proper temperature.
Support the cylinder head and drtve the valve guides
out of the cylinder head from the combustion chamber
side.
TOOL:
Valve guide dri ver, 4.S mm 07942· MA60000
DRIVER
9-23