9-1
CONSTRUCTION
and
OPERATION
9-1-1 FLOAT
SYSTEM
The float chamber is located just below carburetor main body and serves to maintain the fuel level at a constant height by a
joint action of float
(F)
and needle valve
(NV)
incorporated. The fuel flows from the fuel tank into float chamber via needle
valve, which is kept open while the fuel level is low, but closed when the fuel level reaches a predetermined level causing the
float to move up.
9-1-2
THROTTLE VALVE
The throttle valve is operated by the control lever and controls the amount
of
air-fuel mixture and controls engine output
power.
The richness
of
mixture or the air-fuel ratio is automatically regulated at the optimum valve regardless
of
the throttle valve
position.
9-1-3
CHOKE VALVE
The choke valve is operated by the choke lever and when it is closed, the air-fuel mixture becomes rich, and as it is opened
the more, the leaner will be the mixture. The choke system serves to facilitate start-up in cold season. When engine is
cranked with choke closed, the negative pressure to main nozzle increases to introduce fuel in large quantities to make
start-up easy.
9-1-4
PILOT SYSTEM
and
MAIN SYSTEM
This pilot system feeds fuel to engine during idle and slow speed operation.
The fuel fed through main jet
(MJ)
is measured by pilot jet
(PJ),
mixed with air measured by pilot air jet
(PAJ),
regulated
by pilot screw, and then fed to engine through pilot outlet
(PO)
and bypass
(BP).
The fuel
is
mainly fed from pilot outlet
(PO)
during idling.
This main system feeds fuel
to
engine during medium and high-speed operation.
The air measured
by
main air jet (MAJ) is mixed into fuel through bleed holes
of
main nozzle
(MN)
and discharged
to
main
bore
(MB)
as
atomized fuel where it is mixed with intake air through air cleaner to become an optimum air-fuel mixture to
be supplied to engine.
9-2
DISASSEMBLY
and
REASSEMBLY
(Fig.
9-2)
Besides mechanical failures, most trouble are caused. by incorrect mixing ratio. The most common causes
of
such incorrect
fuel-air mixtures are clogged jets, restricted air and fuel passages, and variations in fuel level, In order to obtain the full
performance of carburetor, it is necessary
to
keep air cleaner and carburetor clean
so
that air and fuel flow without any
restriction.
Observe following disassembly and reassembly procedures. (see Fig.
9-2)
CAUTION: AFTER DISASSEMBLY, CLEAN ALL PARTS
IN
A SUITABLE SOLVENT, ALL JETS AND VALVES
SHOULD BE BLOWN OUT WITH FRESH COMPRESSED AIR, NEV€R USE A DRILL OR WIRE TO CLEAN OUT
JETS OR IDLE HOLES.
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