(2) PILOT JET NOZZLE SYSTEM
The pilot jet nozzle system controls the fuel supply for engine speeds ranging from idle to low-speed running.
The system operates with the fuel flowing through the main jet nozzle and up to the pilot jet nozzle where
the fuel is measured. When the fuel is mixed with air, the volume of the air-fuel mixture is also measured
by the pilot air jet. From this stage, the mixture is supplied to the engine from the pilot outlet and bypass.
During idle, fuel is supplied mainly from the pilot outlet.
(3) MAIN JET
NOZZLE
SYSTEM
The main jet nozzle system supplies fuel for middle and high speed operation. The fuel flows to the main jet
nozzle where the fuel quantity is measured, and then flows to the main nozzle. Air volume, which is measured
by the main air jet, enters from the breath hole of the main nozzle and mixes with fuel to form a gas mist.
The gas mist flows out of the main bore and is again mixed with air from the air cleaner. From this stage, the
correct air-fuel mixture is supplied to the engine.
(4) CHOKE
The choke helps in starting the engine in cold weather.
When the engine is started with the choke valve closed, negative pressure applied to the main nozzle rises,
allowing most of fuel to flow through the main nozzle.
A mixture with a high gasoline concentration is fed to the engine resulting in easier engine starting.
10-5-2 DISASSEMBLY AND ASSEMBLY OF CARBURETOR
The most common trouble with the carburetor is failure to provide the correct air-fuel mixture. This is gen-
erally caused by blockage in the air and fuel passages, at other times it is caused by fuel level fluctuations in
the float chamber. In order to maintain the carburetor in normal operating condition, it is vital that the air
and fuel passages be kept clean. The following descriptions are the procedures for carburetor disassembly and
assembly. (See Fig. 10-33.)
(1) THROTTLE MECHANISM
a) Remove Philips-head screw (27), throttle valve (28) and pull out the throttle shaft (29).
b) When removing the throttle stop screw, a spring (3 1) will also come off. Be careful when handling the
throttle valve to prevent the valve edge from damage.
(2) CHOKE
a) Remove Philips-head screw (22), choke valve (23), and pull out choke shaft (24).
b) Be sure to keep the notch of the choke valve positioned forward the main air jet side when the choke
shaft is installed.
(3) PILOT JET
NOZZLE
a) Remove pilot jet nozzle (21). When removing, use a proper tool so that the nozzle will not be damaged.
b) Firmly secure the jet nozzle when the carburetor is assembled. Otherwise, fuel will leak from the nozzle
and cause engine trouble.
(4) MAIN JET
NOZZLE
a) Remove bolt (15), and float chamber body (13).
b) Remove main jet nozzle (19) from carburetor body (9).
c) Firmly secure the main jet nozzle when assembling. Otherwise, air-fuel mixture will become excessively
rich and the engine will not operate properly.
d) Torque for bolt (15) is 70 kg-cm.
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