6-1
-1
FLOAT SYSTEM
The float chamber
is
located just below the carburetor body and, with a float and a needle valve, maintains a constant fuel
level during engine operation.
The fuel
flows
from the fuel tank into the float chamber through the needle valve. When the fuel rises to a specific level, the
float rises; and when its buoyancy and fuel pressure are balanced, the needle valve close to the shut off the fuel, thereby
keeping the fuel at the reference level.
6-1
-2
PI
LOT SYSTEM
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 outllet and the by-pass.
During engine idling, the fuel is mainly fed from the pilot outlet.
6-1-3
MAIN SYSTEM
The main system feeds the fuel to the engine during 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.
6-1
-4
CHOKE
The choke is used for easy start in the cold season. When the recoil starter
is
pulled with a closed choke, the negative pres-
sure applied to the main nozzle increases and draws much fuel accordingly; thus easily start up the engine.
6-2
DISASSEMBLY
and
REASSEMBLY
Apart from mechanical failures, most of carburetor troubles are caused by an incorrect mixing ratio, which may arise mainly
due to a clogged up ah or fuel passage in jets, or fuel level variations. In order to assure proper flow of air and fuel, the car;
buretor must be kept clean at all times. The carburetor disassembly and reassembly procedures are as follows: (See Fig.
49.)
6-2-1
THROTTLE SYSTEM
1) Remove the Phdlips screw
(I)
and throttle valve
(2),
and pull
out
the throttle shaft
(3).
2)
The spring
(5)
can be taken out by removing the throttle stop screw
(4).
*Be careful of the direction
of
the throttle valve.
The circumference of the throttle valve is aslant. Install the valve
so
the punched mark on the valve can be seen on the
left.
6-2-2
CHOKE
SYSTEM
I)
Remove the Phillips screw
(6)
and choke valve
(7),
and pull out the choke shaft
(8).
Stop ring
(9)
can not be removed.
2)
When reassembling the choke shaft, make sure that the cutout in the choke valve faces the main air jet.
''
6-2-3
PILOT SYSTEM
I)
Remove the pilot jet
(1
0),
using correct tool to avoid damage to it.
2)
Remove pilot screw
(1
1)
and spring
(1
2).
3)
Reassembly
*Tighten the pilot jet securely. Otherwise, the fuel may leak, causing engine malfunction.
*If the tapered part of the pilot screw is out
of
shape, replace it with
a
new one.
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27
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