Suzuki Intruder 1978 Service Manual page 36

The fuel level affects how rich or lean the engine
will run throughout its entire range . The reason for
th is is the drop in pressure that occurs in the
venturi. The float bowl is vented to the atmos -
phere, so there is a pressure of 1.03 kg-cm (14 .7
ps i) pushing down on the surface of the fuel in the
float bowl. When the engine is stopped, th is pres -
sure is on the surface of all the fuel in the float
bowl, includ ing the fuel inside the "feed tubes"
which lead into the venturi. When the engine is
running, the pressure in the venturi is less, and
the pressure in the feed tubes is also less . The
atmospheric pressu re acti ng on the su rface of the
fuel in the bowl is much greater than the pressure
acting on the fuel in the feed tube . Therefore, the
level of fuel i n the feed tube rises, push ing the fuel
in the feed tube up into the ventur i where it is re-
leased into the air stream as tiny droplets. (See
Figure 2-18.)
The float level is important at low speeds . If too
low, the decreased pressure in the ventur i would
not be able to pull enough fuel up out of the bowl
and into the air stream. This would cause hard
starting and lean mixture ratios. If the fuel level is
too high, too much fuel is pulled into the venturi
and the engine would run too rich. The float level
is adjusted by bending the tab. Bending the tab
towards the needle valve lowers the fuel level, and
bending it away from the valve raises the level.
Always set the fuel level at the correct level.
Metering the fuel and air in the proper amounts is
performed by a number of separate' systems. Each
system has a range of throttle positions in which it
is effective, but the division between where one
system takes up and another leaves off is gradual.
This "overlap" insures the transition from one
MAXIMUM
PI LOT SYSTEM
THROTTLE SLI DE
VALVE
REDUCED PRESSURE
..
A IRFL
t
Figure 2-18
FUEL
LEVEL
system to another w ill be smooth. The metering
components are the throttle slide, main fuel sys-
tem, pilot system, econo jet system, and starter
system. Figure 2-19 illustrates the overlap be-
tween the components .
I
CUTAWAY
JET NEEDLE/NEEDLE JET
EFFECT
MINIMUM 0
1/8
1/4
2-16 THEORY OF OPERATION
3/8
1/2
THROTTLE POSITION
Figure 2-19
3/4
FULL