Aeon AT56-69E, Service Manual

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FUEL AND CARBURETOR
6-12
HIGH SPEED CIRCUIT SLIDE POSITION AND
FUEL DISCHARGE
As the throttle plate is opening, the pressure difference
between the chambers above and below the diaphragm
increases and the vacuum piston moves further upward.
The venturi opening increases and the needle is lifted feather
out of the needle jet. The quantity of fuel and the volume of air
are simultaneously increased and metered to the proportions of
engine demand by the variable venturi and needle lift. With the
vacuum piston fully upward, the venturi opening is fully
enlarged and the needle jet opening exposure to the air stream
is at its maximum. Air and fuel supplies are now available in
quantities sufficient to meet all engine demands.
ACCELERATIVE PUMP SYSTEM
The accelerator pump used sudden throttle openings (rapid
accelerations) to quickly inject fuel into carburetor venturi to
provide extra fuel for smooth acceleration. This fuel also
assists engine operation during cold engine warm-up when the
enlightener is turn on prematurely.
Rapid throttle action during the first third of throttle travel
pushes the pump rod down, flexing a diaphragm. This flexing
action force fuel past a check valve into the stroke. A spring
then returns diaphragm to its original position and a new
supply of fuel flows in under the diaphragm from the float
chamber for the next acceleration.