The Monojet carburetor is a single bore downdraft carburetor that has a triple venturi coupled with a refined metering system resulting in a unit with superior fuel mixture control and performance. A plain tube nozzle is used in conjunction with the triple venturi. Fuel flow through the main metering system is controlled by a mechanically and vacuum operated variable orifice jet. This consists of a specially tapered metering rod, which operates in the fixed orifice main metering jet, connected directly by linkage to the main throttle shaft. A vacuum operated enrichment system is used in conjunction with the main metering system to provide good performance during moderate to heavy accelerations. The Monojet carburetor is designed with either a manual or automatic choke system. The conventional choke valve is located in the air horn bore. A vacuum diaphragm unit is an integral part of the air horn on some automatic choke MV models, and on other automatic choke models the unit is mounted externally to the air horn of the carburetor. The automatic choke coil is manifold mounted and connects to the choke valve shaft by a rod.