SECTION 3
3-10
1-/ 2-Cylinder
Fuel Pump
The fuel pump may be integral with the carburetor or
mounted on the side of the crankcase and contains one or
more internal diaphragms
(1)
. The diaphragms move in response to
changing crankcase pressures
(2)
which draws fuel in
(3)
and
pumps fuel out
(4)
. A series of check valves
(5)
in the pump ensure
that fuel moves only in one direction.
Carburetors
The carburetors use a pilot system and main system to meter and
deliver an atomized fuel mixture to the engine for combustion under
varying operating conditions.
Pilot System
The pilot system is a slow speed system consisting of the slow
jet, slow air jet, pilot outlet, bypass, and pilot adjusting screw.
At 1/4 throttle and less, mixed fuel
(1)
enters the carburetor and flows
from the carburetor float chamber
(2)
through passage
(3)
to the pilot
jet
(4)
. Air
(5)
measured at the pilot air jet
(6)
is directed through
passage
(7)
and combines with the existing fuel from the pilot jet to
form fuel/air mixture
(8)
. After exiting bypass
(9)
, the mixture directly
enters engine
(10)
or passes pilot adjustment screw
(11)
for output to
the engine through pilot outlet
(12)
. Unrestricted air flow to the engine
is available through venturi
(13)
.
T1003
3
3
4
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