BING CONSTANT DEPRESSION CARBURETTOR
TYPE 64-3
The BING constant depression carburettor type 64-3 comprises a cross draught butterfly-valve carburettor with variable choke tube, independent double-float system arranged centrally below the carburettor venturi and a rotary-valve type starting carburetor. 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.
The throttle valve diameter is 36 mm.
MOUNTING
The carburettor is secured to the engine using a 43mm 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 50 mm and a length of 12 mm for connecting an air filter or intake silencer.
FUEL INTAKE CONTROL
The floats of the carburettor consists of two plastic float elements which actuate a metal hinge. The floats are 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 constant. When fuel has reached a specified level in the float chamber, the floats, which are mounted on posts, are lifted until the float needle 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 drops and so does the floats. 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 floats 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 the 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 grater than 0.1mm are filtered out and the fuel supply is not impeded to too great an extent.
The float needle contains a spring-loaded plunger which contacts the float hinge. This absorbs vibrations on the float. In addition the float needle is connected to the float hinge by the retaining spring 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 arm just contacts the float needle. In this position the point on the float hinge is set in such a way that the float arm top edges are parallel to the top edge of the float chamber with a distance of 10.5mm or .412 inch.
The float chamber is...
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