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Adjustments for Competition 111
Carburetor Adjustments & Tuning Tips
Accelerator Pump Circuit
The accelerator pump circuit operates when the
throttle is opened. As the throttle valve (1) opens,
the pump rod (2) depresses the diaphragm (3). At
this time, the inlet check valve (4) is shut
resulting in a sharp increase in pressure in the
pump chamber (5). The outlet check valve (6)
then opens, supplying fuel to the main bore via
the accelerator nozzle (7). Leak jet (8) operation
is related to both the length of time before the
fuel starts flowing after the opening of the
throttle (time lag) and the flow amount.
(1) throttle valve (5) pump chamber
(2) pump rod (6) outlet check valve
(3) diaphragm (7) accelerator nozzle
(4) inlet check valve (8) leak jet
Slow Circuit
Fuel is metered by the slow jet (1) and mixed
with air from the air passage (2). The mixture
enters the venturi through the bypass (3) and
pilot outlet (4) that has been metered by the pilot
screw (5).
(1) slow jet (4) pilot outlet
(2) air passage (5) pilot screw
(3) bypass
Main Circuit
Fuel is metered by the main jet (1), jet needle (2)
and needle jet (3). It is then mixed with air
coming from the air jet (4) and enters the venturi
past the needle jet.
Baf
fle Plate
The baffle plate (5) prevents foaming of fuel or
abnormal fuel level around the mainjet.
Float Bowl
The float (6) and float valve (7) operate to
maintain a constant level of fuel in the float
bowl.
(1) main jet (5) baffle plate
(2) jet needle (6) float
(3) needle jet (7) float valve
(4) air jet
(1)
(8)
(7)
(6)
(2)
(5)
(4)
(3)
(3)
(2)
(1)
(5)
(4)
(4)
(2)
(7)
(1)
(3)
(5)
(6)
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