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ZENITH CARBURETTER
Cleaning and Adjustment for good
Performance
T
HE carburetter fitted to the Austin Seven is the Zenith "V" type,
embodying the well known principles, of main and compensating
jets.
Pelrol from the pump passes through the union, the filter and the
needle seating into the float chamber. As the float rises it will close the
needle on its seating, thus regulating the flow of the petrol.
The float chamber contains the main jet, the compensating jet, the
capacity well, and the slow running jet. Petrol flows through the main
and compensating jets and also rises in the capacity well. From the jets
it flows along two separate channels into a common channel in {he emulsion
block attached to the float chamber. This main channel has its outlet
in a nozzle which projects into the choketube.
Tbe capacity well is in direct communication with the atmosphere,
and the compensating channel in the emulsion block.
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Starting the Engine.
To obtain an easy start from cold the combined throttle and strangler
control on the dashboard should be extended to its third position, and the
engine should be given, by hand, a few turns to free the working parts.
Then pull the self-starter control knob and when the engine is running
release the strangler control to the first notch.
In cold weather it may be, necessary to hold the strangler control
out for a few minutes while the engine warms up, and to run the car for
the first few minutes with the knob in the first notch, As soon as the
engine is warm, however, the control knob should be pushed right in,
otherwise the mixture will be too rich.
If difficulty in starting the engine is experienced, ascertain that the
strangler flap is closing properly and if necessary adjust the wire.
A choked slow running jet will also cause difficulty. The jet should
be cleaned only by blowing through it, either with a tyre pump or orally.
Trouble can also be experienced if the throttle is not open sufficiently
when the strangler knob ,on the dash is in the first notch. In this case
turn the adjusting screw a little to the right to open the throttle wider. '
If the engine does not idle as slowly as desired, turn the screw to the
left to close the throttle slightly,
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A weak mixture may cause difficulty in slow running and this may be
adjusted by turning the regulating screw clockwise to enrich the mixture,
Do not make the mixture too rich or the engine will "hunt," or will tend
to choke when slow running while warm,
Adjustments.
No adjustments should be carried out unless absolutely necessary.
If the engine is positively poor in accelerating when it is running at a
sufficiently warm temperature, and the adjustments described will not
remedy the trouble, it may be desirable to fit a larger compensating jet.
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The V Type Carburetter (without Air.Cleaner).
A-Pmol Union
B-Union Nm
C-W"h",
D-Rm,ning Bol"
E-Adjo."n, Smw
F-R"olo"ng Smw
If there is a lack of power and speed, this may be due to the main jet
being partially choked, or if greater power is desired a larger size rrlliin jet
may be fitted.
Make sure that the strangler flap opens fully, for if this sticks in a
partially closed position it will restrict the speed of the car and increase
petrol consumption.
Do not, however, alter the jets unless you are quite sure that other
parts of the engine, including sparking plugs, ignition and valves are in
order, and that compression is good. There are no moving parts in the
Zenith carburetter, so that nothing can get out of adjustroent when once
set.
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