Suzuki Intruder 1978 Service Manual page 41

Econo (Power) Jet System
The econo jet system is sim il ar to the ma in system
in that it only draws fuel when there is enough air
flow through the venturi to draw fuel through the
system. The fuel that passes through the system is
metered by a reverse type jet . Th is system has the
most effect during wide open throttle position
when the engine is operating at engine speeds
above 5000 RPM . Use of econo jet gives better
engine response at high engine speeds (over 5000
RPM) and better fuel economy at lower engine
speeds. At\7Vi-ae open throttle the main jet sup-
plies approximately 70% of the engine fuel re-
quirements while the econo jet supplies 30%. The
econo jet stops feeding fuel below 1/ 2 throttle or
5000 RPM due to the reduced air flow through the
carburetor bore at low throttle settings .
Pilot System (See Figure 2-29 .)
Fuel and air supply at low speeds and small
throttle openings is controlled by the pilot system,
or slow system . The pilot system consists of a
series of passageways in the carburetor body, a
pilot jet to meter fuel, and a pilot air screw to
meter air. At low engine speed and small throttle
open ing the main system can not provide the
proper amount of fuel or air.
Fuel is drawn through the pilot jet which pro-
trudes into the float chamber. The pilot jet has a
series of holes drilled in its body at the point
where the air is introduced from the passage-
ways. These holes allow fuel to be mixed with air
before it enters the ventur i through the pilot outlet .
(See Figure 2-30.)
Air for the pilot system enters from the front of the
carburetor and is metered by the pilot air screw.
The pilot air screw is tapered to provide a gradual
increase in air flow as the screw is backed out.
The taper fits in the center of a passageway, and
turning the screW all the way i n closes the
passageway. The normal air screw setting is from
1 to 1-3/ 4 turns out from a lightly seated position.
If the pilot mixture appears too rich, backing the air
screw out further will lean the mixture . Turning
the air screw in farther will cut down the amount
of air supplied, resulting in a richer mixture . Ad-
justment of pilot mixtures can also be effected by
changing pilot jets.
At idle speeds (very low, "closed" throttle posi-
tion) air from the air passage in the front of the
carburetor is supplemented by air from the pilot
bypass . At these almost c losed throttle settings, air
enters from the pilot air passage and the bypass .
When the throttle is opened, air flow through the
venturi increases, and fuel / air mixture now exits
from both the outlet and the bypass, where it
mixes with the air flowing through the venturi.
V ENTURI
THROTT LE
AIR FLowt
PILOT AIR SCREW
SLIDE PILOT BYPASS
VENTURI
.. ?;F:"
AIR F LOvVPRESSURE
Figure 2-29
PI LOT JET
Figure 2-30
PILOT
UTLET
/.
PILOT
BYPASS
~
PILOT JET
THEORY OF OPERATION 2-21