High
Speed
When the engine is operating with the throttle
lever in the "Fast" position, the fuel flows as
follows:
When the intake port is opened by the
piston skirt, a partial vacuum is created in the
engine crankcase.
Atmospheric pressure pushes air through the
venturi causing a drop in pressure at the venturi
throat. It also pushes fuel through the main jet
and up the inside of the nozzle.
Atmospheric pressure pushes air through the
main air jet to the outside of the nozzle.
The air then enters through the nozzle bleed
holes and mixes with the fuel coming up the
inside
of
nozzle.
This air/fuel mixture is pushed up and out of the
nozzle into the incoming air stream at the ven-
turi and into the engine through the intake port.
The throttle valve controls the amount of air/fuel
mixture entering the engine,
as
the governor
responds to changing operating loads.
Choke
The choke valve is closed when starting a cold
engine.
When the piston skirt opens the intake
port, a partial vacuum is created in the carbure-
tor behind the choke valve. Atmospheric pres-
sure pushes air through the air jets in the carbu-
retor body and fuel flows
as
described in "Idle
Speed" and "High Speed" together for
a
very
rich mixture.
2-3
Pilot
Jet
Pilot
Air
Jet
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