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60
3.
ENG I NE
CD
®
Fig. 3. 126
Main jet, needle jet holder, and needle jet
CD
Main jet
®
Needle jet holder
®
Needle jet
< >
CD
Fig. 3.
127
CD
Gasket
®
Valve seat
®
Valve
@
Float
@
from the needle jet.
(Fig. 3. 126).
When the
vacuum piston is fully closed (when it works as the
primary venturi) or when the vacuum piston is half
closed, the tapered portion of the jet needle instal~
led on the vacuum piston ( 1 6) squeezes the fuel
in order to prevent excessive fuel passage from
the needle jet. (Fig. 3. 124)
3.
Float chamber
The carburetor must produce mixtures suitable for
individual throttle opening and individual engine spe-
ed, and for this purpose, the fuel level must be
maintained at a constant level.
The float chamber
performs this function.
The fuel coming from the fuel tank enters into
the float chamber through passage from the fuel
tank, float valve seat, and float valve.
The float
( 11 l is floated up accordingly with the fuel entry,
float valve (6) is lifted by the float arm (7), and
when the float valve (6) contacts the float valve
seat (5). the fuel inside the float chamber (9) is
used, and the fuel level is lowered, the float (11)
is also lowered accordingly, the float valve (6)
leaves the float valve seat (51 ; thus, the fuel enters
into the float chamber (61.
By repeating these
operations, a constant fuel level can be maintained.
The portion of float valve (6) which contacts float
arm
(7)
is provided with spring to increase the
durability against vibration (Fig.
3.
127).
Further,
when the motorcycle is inclined or foreign matter
sticks to the float valve seat, fuel overflows, and
the fuel enters the cylinder ; thus, the overflow line
(8) has been provided to maintain the specific fuel
level.
When the fuel level reaches a specific
level, the overflow line permits the fuel to be dis-
changed.
(Fig. 3. 123)
4.
Choke
When starting engine in cold weather, it is neces-
sary to provide a rich mixture, and for this purpose,
choke valve (3) has been provided.
When the
choke lever ( 17) is raised, the choke",{3) closes and
air flow is limited ; thus; the fuel injected from the
needle jet is inhaled by the engine as rich mixture
as it is.
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