Honda CB350 Repair Manual page 61

56
ENGINE AND TRANSMISSION
moved, the valve.should come right out
of .the—guidew—Any—sticking.or binding as
the—valveris=removed. will indicate—that
the valverstem —or the guide is in bad.con—
dition.
9. Inspect the valve paying close at—
tention to the condition.of.thesedges of
the valve head for pitting, burnt or bro—
ken edges, excesSsive=carbon "Build=up,
etc. A certain amount of carbon build—up
on the valve face and on the top of the
BADLY BURNT VALVE
Decarbonizing the valve
Carbon deposits should not extend too far up along
the stem or a worn guide is indicated
exhaust valve head is inevitable. These
deposits Should=bencarefully=seraped off
with a dull knife or with=a"Wwire wheel,
and the valve finished with a fine—emery
eloth. Take care not to score the valve
stem.
Carbon deposits, however, should=not
extend too far up along theexhaustwalve
stem. This would indicate a worn or
cracked valve guide.
Wet oil on the back of the valve head is
indicative of a worn guide (which must
be replaced) or a bad valve seal (360).
10. ~Oilsthe valve stem with motor=0il
and insert it"into0 its—guide. Holding the
valve away from its seat about % in., spin
the valve stem with your fingers and
watch the head of the the valve
is hard to rotate orif the head ofthe valve
wobbles, the valve is bent and must be
replaced.
An engine will run with a bent valve;
these valves even have a fair sealing abil—
ity occasionally, so close inspection is
always imperative.
A bent valve must always be replaced
and, if one is foundit is. wise to inspect
the guide very carefully, as it is very
likely to be cracked. Also inspect the pis—
ton crown very closely as it is likely that
the valve was bent by hitting the piston.
Often when this happens the ring
grooves will be compressed andis an in—
dication that a valve may be bent.
11. Gheck. the diameter=of the. valve
stem—with a micrometer—against the val—
ues given in the {Engine Specifications'
charts at the end ofthis chapter. If a valve
Checking valve stem diameter