4-12 FUEL SYSTEM
MAIN SYSTEM
As the throttle valve 1 is opened, engine speed rises and negative pressure in the venturi A increases. This
causes the piston valve 2 to move upward.
The fuel in the float chamber 3 is metered by the main jet 4. The metered fuel enters the needle jet 5, mixes
with the air admitted through the main air jet 6 and forms an emulsion.
The emulsified fuel then passes through the clearance between the needle jet 5 and jet needle 7 and is
discharged into the venturi A, where it meets the main air stream being drawn by the engine.
Mixture proportioning is accomplished in the needle jet 5. The clearance through which the emulsified fuel
must flow ultimately depends on throttle position.
AIR
FUEL/AIR MIXTURE
FUEL
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