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8-1
-1
FLOAT SYSTEM
The float system is consists of
a
float and a float valve, and maintains a constant fuel level during engine
~
operation.
The fuel flows from the fuel tank into the float chamber through float valve.
When the fuel rises
to
a specific level, the float rises, and when its buoyancy and fuel pressure are
balanced, the float valve closes to shut
off
the fuel, thereby keeping the fuel at the predetermined level.
8-1-2
PILOT
SYSTEM
The pilot system feeds the fuel to the engine during idling and low-speed operation.
The fuel is fed through the main jet to the pilot
jet,
where it is metered, and mixed with the air metered by
the pilot air jet.
The fuel-air mixture is fed into the combusion chamber through the idle
port
and the
slow
port.
At idling speed, the fuel is mainly fed from the idle port.
8-1-3
MAIN
SYSTEM
The main system feeds the fuel
to
the engine at medium-and high-speed operation.
The fuel is metered by the main jet and fed to the main nozzle. The air metered by the main air jet is
mixed
with
the fuel through the emulsion hole, and the mixture is atomized out of the main bore.
It
is
mixed again with the air taken through the air cleaner into an optimum fuel-air mixture, which
is
supplied
to the combusion chamber.
8-1
-4
CHOKE
The choke
is
used for easy start when engine is cold.
When the starter
is
operated with a choke valve fully closed, the negative pressure applied to the main
nozzle increases and draws much fuel accordingly; thus easily start up the engine.
8-1-5
ACCELERATOR-PUMP SYSTEM
When the throttle is opened rapidly for acceleration, air flow and manifold vacuum change almost instan-
taneously. Because fuel is heavy and lags behind air flow, a momentary leaness results. The accelera-
tor-pump suplies extra fuel for smooth operation during this condition.
At constant load condition, a vacuum passage in the carburetor applies manifold vacuum to the pump
diaphragm and the pump diaphragm is held to pull position.
When the throttle is opened rapidly for acceleration, the manifold vacuum is droped, the pump dia-
phragm moves by the diaphragm spring, the fuel in the pump chamber push out by the pump diaphragm
and the fuel gush out from the accelerator-pump nozzle.
8-1
-6
FUEL
CUT
VALVE
Fuel cut valve, operated with starter key switch,
is
equipped with main system of carburetor for prevent-
ing engine running on and after burning.
When the key switch is
on,
the valve is activated and the plunger is pulled in to open the main jet.
When the key switch is
off,
the power source to the valve is
off.
The plunger is pushed out by the retum
,-
spring
and stop the fuel flow of main jet.
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