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Carburetor Adjustments & Tuning Tips
Adjustments for Competition
111
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.
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).
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.
Baffle Plate
The baffle plate (5) prevents foaming of fuel or
abnormal fuel level around the main jet.
Float Bowl
The float (6) and float valve (7) operate to maintain
a constant level of fuel in the float bowl.
(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
(1)
(8)
(7)
(6)
(2)
(5)
(4)
(3)
(1) slow jet (4) pilot outlet
(2) air passage (5) pilot screw
(3) bypass
(3)
(2)
(1)
(5)
(4)
(1) main jet (5) baffle plate
(2) jet needle (6) float
(3) needle jet (7) float valve
(4) air jet
(4)
(2)
(7)
(1)
(3)
(5)
(6)
31KSE7100_NA.book 111 ページ ２０１９年４月９日 火曜日 午後１時１３分
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