Automatic Admission of Secondary Air.—If the engine should be speeded up so twice the amount of oil is drawn into the mixing chamber, the additional suction will not, at the same time, draw in twice the amount of air.
This necessitates a provision whereby the secondary air shall be admitted automatically only at times when the suction exceeds the normal requirement, or to prevent too rich a mixture, which is explained by reference to Fig. 80.
Fig. 81. Carbureter Secondary Air Inlet.
The extension S, on the right side of the shell, has an opening T, with a seat to receive a weighted valve, like a ball U, preferably reinforced by a spring V, which is capable of having its pressure on the seat regulated by an adjusting screw W.
It will be obvious, therefore, that during the normal action of the engine suction, no air will enter the duct T; but when an undue vacuum exists in the chamber O, the ball valve U is raised, and additional air is supplied to the carbureted air within the chamber.
Fig. 82. Complete Carbureter.
Carbureter Adjustment.—Each of these four elements has some particular method of adjustment, as will be more particularly noticed in the completely assembled carbureter, made up of the foregoing illustrations, in which the details are refined and shown as actually made in one of the well known types of carbureters.
Fig. 82 shows the different parts arranged in a practical manner, in which the regulating arm for controlling the throttle, as well as the secondary air supply and the gasoline inlets are capable of being adjusted by special means.