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8-1-2
PILOT SYSTEM
n
The pilot system feeds the fuel to the engine during idling and low-speed operation. The fuel is fed
through the main jet
to
the pilot jet, where it is metered, and mixed with the air metered by the pilot air jet.
The fuel-air mixture is fed to the engine through the pilot outlet and the by-pass. At idling speed, the fuel
is mainly fed from the pilot outlet.
8-1-3
MAIN
SYSTEM
The main system feeds the fuel to the engine at medium and high-speed operation. The fuel is metered
by the main jet and fed to the main nozzle. The air metered by the main air jet is mixed with the fuel
through the bleed holes in the main nozzle, and the mixture
is
atomized out of the main bore. It is mixed
again with the air taken through the air cleaner into an optimum fuel-air mixture, which
is
supplied to the
engine.
8-1
-4
CHOKE
The choke is used for easy start when engine is cold. When the starter is operated with a closed choke,
the negative pressure applied to the main nozzle increases and draws much fuel accordingly
;
thus
easily start up the engine.
8-2
DISASSEMBLY AND REASSEMBLY
Apart from mechanical failures, most of carbure-
tor troubles are caused by an incorrect mixing
ratio, which may arise mainly due to a clogged up
air
or
fuel passage in jets, or fuel level variations.
In order to assure proper flow of air and fuel, the
carburetor must be kept clean at all times. The
carburetor disassembly and reassembly proce-
dures are
as
follows.
8-2-1
THROTTLE SYSTEM
(1
)
The spring
(4)
can be taken out by removing
the throttle stop screw
(5).
(2)
Remove the Phillips screw
(1)
and throttle valve
'
(2),
and pull out the throttle shaft
(3).
*Exercise care not to damage throttle valve ends.
12311
19
21
13
18d
l2
-
Fig.
8-3
-
48-