Classic Cycles Technical Resources
45
The air jet controls the flow of air entering the needle jet. The fuel passing through the needle jet mixes
with the air coming in from the air jet.
(3) Needle Jet
At full throttle or at medium speeds, the fuel is first regulated by the
main jet and the needle jet acting simultaneously.
(4) Jet Needle
The tapered jet needle attached to the throttle valve works in the needle jet and adjusts the air/fuel ratio at
medium (¼ to ¾) throttle openings.
(5) Throttle Valve
The throttle valve is cut away on the
inlet side and controls the flow of
main fuel supply from c to ¾ throttle
opening. The extent of cut away is
marked on the valve, viz. 2.0 for
2.0m/m cut away.
(6) Pilot Jet
At idling speed or small throttle
openings, the pilot jet controls the
flow of fuel mixed with air which enters through the air jet, and atomizes the
mixture.
(7) Air Screw
The air screw controls the flow of air which mixes with the fuel passing
through the pilot jet.
The standard adjustment of this screw position for the various models
is stated below under Adjustment (3).
C. Adjustment:
Carburetors on all models are factory adjusted for proper operation
and idle. In the event idle adjustment is
necessary, proceed as follows:
(1) Run engine for at least 3 minutes in a properly ventilated area. Idle cannot
be correctly adjusted on a cold engine.
(2) Turn idle mixture adjusting screw in clockwise as far as it will go.
CAUTION: DO NOT OVER-TIGHTEN!
(3) Turn idle mixture adjusting screw counter-clockwise the number of turns
indicated below:
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