Dirt in the fuel may lodge in the float valve
and cause an overrich mixture. As a temporary
measure, tap the carburetor lightly to dislodge
the dirt. Clean the fuel tank, fuel tap, fuel line
and carburetor at the first opportunity should
This book covers U.S. models subject to
emission control laws. These laws
subject motorcycle dealers and their
employees to heavy fines for modifying
emissions related components. Although
Federal law does not cover modification
by the motorcycle owner, some states
have laws that prohibit emission-related
modifications by owners. Check the laws
in your area before you change
Do not try to solve a problem by rejetting if
all the following conditions hold true.
g. T h e motorcycle has never held a
satisfactory engine tune.
The original jets and jet needle numbers are
1 at the end of this chapter.
The following parts of the carburetor can be
changed to alter the fuel mixture. Each part has
the most effect over a narrow range of throttle
openings, but each also has a lesser effect over
a broader range of throttle openings.
Pilot Jet and Screw
The pilot jet and idle mixture setting affect
to about 1/8 throttle. As pilot
jet numbers increase, the fuel mixture gets
richer. As the idle mixture screw
(turned out), the mixture gets leaner.
On motorcycles sold in the U.S., the idle
mixture screw is sealed under a plug.
The throttle slide cutaway
3/4 throttle. The grooves at the top of the jet
Rejetting the carburetors may be required if
adjustment of the
any of the following conditions hold true.
As the clip is raised (and the needle drops
a. A nonstandard air filter element is being
b. A nonstandard exhaust system is being
c. Any of the t o p e n d parts (piston,
camshaft, compression ratio, etc.) have
d. The motorcycle is in use at considerably
higher or lower altitudes or in a markedly
hotter or colder or wetter or drier climate
than in the past.
e. The motorcycle is being operated at
considerably higher speeds than before
and changing to colder spark plugs does
not solve the problem.
f. Someone has changed the jetting or the
needle position or number on your
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