Lapping - Honda CB350 Repair Manual

58 ENGINE AND TRANSMISSION
LAPPING
1. Valves should—be"lapped into their
seats if the leakage test shows poor seal—
ing, if the edges ofthe valve or the seat in
the head are pitted, if the motorcycle
has covered considerable mileage, or if
new valves or guides are fitted.
2. Clean off all—of the—carbon.build—up
onthe surface of the—combustion—cham—
bersPlace three small._dabs—of valve lap—
ping paste around the.circumference of
the —valve head and place. the —valve~into
the guide. Be sure to coat the valve stem
with—oil before inserting it into the guide.
3. If you have a lapping tool, use it as
the manufacturer directs. Usually, the
tool will turn the valve back and forth
while rotating it around the seat at the
same time. Do not use excessive pressure
during the operation.
Applying valve lapping compound to the walve
A lengthsof fuel line will serve,in' place of a lap—
ping tool
If you do not have such a tool, a thick
piece of fuel line placed over the valve
stem works just as well. Furn the valve
back and forth and rotate it to a new posi—
tion every few seconds.
NOTE: Check the condition of the
valve face and seat frequently. Whena
smooth, even finish is evident, stop
lapping. Excessive lapping may lead to
a pocketed valve.
4" Remove ~the—valve—and—clean it
thoroughly. Remove any traces of lapping
compound from the seat and the combus—
tion chamber=Swab Out the guide with a
cotton swab soaked 'ina "solvent.. Squirt a
little oil into the guide so that it may carry
away any particles inside.
5. «Check the—width—and=condition of
the valve seat. The,.seat:should be about
Lapping the valve