Fuel supply system (Zenith 67/267)
The 67-series and 267-series carburetors are of the single barrel updraft design, with a single venturi, twin floats and a semi-concentric fuel bowl to permit operation at quite extreme angles without flooding or starving the engine. They are of the “balanced” and “sealed” type since all air for fuel bowl ventilation and idle operation must enter through the air cleaner. The fuel supply system is made up of the threaded fuel inlet, fuel valve (needle and seat), float assembly and float chamber.
The idle system in the 67-series consists of the idle discharge port, idle air passage, idle adjusting needle, idle jet and idle fuel passage. In the 267-series, the idle ystem consists of two idle discharge holes, idle air passage, idle air bleed, idle adjusting needle, idle jet and fuel passage.
The high speed (main metering) system consists of the venturi, main jet calibration, well vent and discharge jet. Int he 67-series carburetor, the economizer system consists of a metered slot in the throttle shaft, a vacuum passage connecting the throttle bore with the slot in the throttle shaft and a vacuum passage from the slot in the throttle shaft to the bowl vent channel.
In the 267-series carburetor, the economizer system consists of a drilled hole from the throttle bore into. achannel communicating with the air space in the fuel bowl, and a restriction in the channel venting the fuel bowl to the air intake. The choke system is of the semi-automatic type and consists of a choke plate with a spring loaded poppet valve mounted on a shaft located within the air intake and operated externally by a lever attached to the choke shaft.