|Econ||Abbreviation for "Economy Jet"|
|S.R.||Abbreviation for "Slow Running Jet"|
|C.S.||Abbreviation for "Contract Sheet", Zenith internal use only, always to be quoted in correspondence with Zenith|
|Comp|| Abbreviation for "Compensation jet".
This jet cannot be confused with the "main jet" as the external diameter of the two jets vary, the main jet being
smaller than the compensating jet in diameter. The jets have the same "flow" calculations and are stamped with the
size numbers. The sizes normally follow in stages of "5" , although "half-size" jets are sometimes used. The greater
the number stamped on the jet, the larger is the drilling of the orifice.
|Vent|| Abbreviation for "Ventilation to the capacity well".
In V type carburettors the ventilation is in the screw over the capacity well. Numbers are stamped on the head of
this screw when the size of the hole differs from the standard diameter. In certain carburettors where the capacity well
is cored to the required size and has no loose tube fitted, the top of the well is open and no screw is incorporated.
In 'U' type carburettors the ventilation to the compensating jet is by means of holes drilled
in the head of the slow
The letters 'P.T. and F.T. indicate Part Throttle and Full Throttle ventilation respectively,
where the carburettor has an
|"C" Tube|| Abbreviation for "Capacity Tube"
This is a separate loose fitting in certain types, but in others the capacity well is cored the correct diameter to give the
necessary reserve of fuel for acceleration purposes.
|N & S|| Abbreviation for "Needle & Seating"
The size being stamped on the hexagon of the seating.
|Choke|| Abbreviation for "Choke Tube"
This may be cast the correct size in the barrel of the carburattor or may be a loose detachable fitting. The size
shown on the choke tube indicates the smallest bore of the restricted part in millimetres. Therefore, if the number is
difficult to decipher, a pair of internal callipers will enable the size of the tube or cast restriction in the barrel to be
Normally, the screw retaining the choke tube does not protrude beyond the inner bore of the tube. In some cases,
In 'U' type carburettors no bar was fitted across the choke tube as standard, but it has been used on a few occasions
|Start Device|| On certain 'V' type carburettors a type of starting device was used that employed a spring loaded air valve. The
spigoted end of this valve was fitted with a loose sleeve, the diameter of which is specified on the setting list. The
sleeve was not marked, but the size is the outside diameter of the sleeve in millimetres.
Certain 'U' type carburettors has a
starting valve employing a starting jet only, which screwed into the top face of the
|Prog||Abbreviation for "Progression Jet"|