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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: 64 of 116
L:\files\Manuals_For_Products\Engine_Manuals\Transition\JEM2204-9_I&M_unsigned.docx
Idling should always be with the engine at operating temperature. First the mixture control
screw (7) is turned fully clockwise and then backed off by the number of turns specified for
the particular engine. Turning in clockwise direction results in a leaner mixture and turning
in anti-clockwise direction in a richer mixture.
The idling setting quoted serves as a guide only. The optimum will generally differ slightly.
First select the desired idling speed by using the idling stop screw (34). When
subsequently adjusting the mixture control screw - starting from the basic setting - a speed
drop will be noticed in both directions. The optimum setting will generally be found half-
way between the two settings at which this speed drop was noticed.
To facilitate the idling setting on engines having several carburettors where it is important
that they are evenly adjusted, it is possible to connect a pressure gauge (in the simplest
case a "U-tube pressure gauge") to a nipple below the throttle valve shaft bearing point
which is normally closed off by screw (39). To select the idling speed, the idling screw
(34) is in this case adjusted until the same vacuum is indicated for all carburettors. By
slightly opening the throttle valve via a turning handle or the accelerator it is also possible
to adjust Bowden cables or linkages evenly by making this vacuum comparison.
STARTING CARBURETTOR
BING constant depression carburettor is provided with a rotary valve starting carburettor
as an aid for staring a cold engine using a Bowden cable. A disc (47) resting against the
carburettor housing is turned via a shaft in the starting carburettor housing (48) so that the
starting carburettor chamber into which air enters from the air filter side of the carburettor
is connected to the engine side of the carburettor via a duct. The airport in the disc (47) is
shaped in such a way that depending on the disc position, more or less air is drawn in. At
the same time the disc opens the fuel system of the starting carburettor via bores matched
to the disc position. The fuel flows from the float chamber through the starting jet into the
vented starting chamber also contained in the float chamber (44) and from there through a
riser where it is pre-mixed with air via transverse bores, into the starting carburettor.
There it forms a particularly rich mixture with the air drawn in, and this mixture bypasses
the main carburettor to flow into the intake manifold of the engine direct.
During starting
the throttle valve has to be closed to make sufficient vacuum available for the
starting carburettor.
When the engine is at a standstill and also during normal operation
the fuel level in the float chamber compartment incorporating the riser will be the same as
in the rest of the float chamber. When starting with opened-up starting carburettor, the
fuel will initially be drawn in from this compartment which forms a very rich mixture. The
fuel supplied subsequently will only be the amount allowed through by the starting jet.
This ensures that, once the engine has started, it is not supplied with an excessively rich
mixture and stalled. The starting carburettor is therefore matched to any given engine by
modifying the starting jet and matching the space behind it.
The starting carburettor is secured to the carburettor housing by four screws (51) and
protected against ingress of dirt and water by the seal (50) between the two. The starting
shaft is also sealed against the starting carburettor housing by a rubber ring (49).