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Jabiru Aircraft
Pty Ltd
Instruction & Maintenance Manual
Jabiru 2200 Aircraft Engine
Hydraulic Valve Lifter Models
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REVISION
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Dated : June 2010
Issued By: DPS
Page: 61 of 116
L:\files\Manuals_For_Products\Engine_Manuals\Transition\JEM2204-9_I&M_unsigned.docx
Carburetor Operation
The BING constant depression carburettor type 94/40 comprises a cross draught butterfly-
valve carburettor with variable choke tube, double-float system arranged centrally below
the carburettor venturi and a rotary-valve type starting carburettor. It features a throttle
slide which is suspended from a roller diaphragm and projects into the venturi. It changes
the smallest cross-section ("choke tube") of the venturi as a function of the vacuum at this
point.
Throttle valve diameter is 42mm
Carburetor Mounting
The carburettor is secured to the engine using a 52mm diameter push-on connection
which takes a flexible connecting piece with clamps. On the intake side the carburettor is
provided with a socket having a diameter of 55mm and a length of 12mm for connecting
an air filter or intake silencer.
Fuel Intake Control
The float (40) of the carburettor consists of two plastic float elements joined by a metal
hinge. The float is arranged centrally below the carburettor choke tube so that the
carburettor can be tilted very far in all directions without impairing operation. The object of
the float is to maintain the fuel level in the float chamber (44) constant. When the fuel has
reached a specified level in the float chamber, then the float (40) mounted on pin (41) is
lifted until the float needle (42) is pressed against the seat of the float needle valve, thus
preventing any further supply of fuel. When the engine draws in fuel from the carburettor,
the level in the float chamber (44) drops and so does the float. The float needle then
opens the valve again and allows fuel to flow in from the tank. The float needle valve
regulates the fuel supply in conjunction with the float but it does not act as a stop valve
when the engine is at a standstill. Minute foreign bodies may be deposited between valve
seat and needle tip, thus preventing complete closure of the valve. When stopping the
engine, therefore, the fuel cock on the tank should always be closed. In addition the fuel
should be filtered before it reaches the carburettor. The filter should be selected so that
foreign bodies greater than 0.1mm are filtered out and the fuel supply is not impeded to
too great an extent.
The float needle (42) contains a spring-loaded plunger which contacts the float hinge.
This absorbs vibrations on the float (40). In addition the float needle (42) is connected to
the float hinge by the retaining spring (43) to prevent it from moving between float and
valve seat and thus reducing the fuel supply. Spring and retaining guide make a
considerable contribution towards keeping the fuel level in the float chamber constant.
When fitting a new float, the fuel level must be adjusted. When doing this care must be
taken to ensure that the fuel needle spring is not compressed by the float weight. It is
therefore advisable to put the carburettor in a horizontal position until the float just
contacts the float needle. In this position the point on the float hinge is set in such a way
that the float top edges are parallel to the top edge of the float chamber.