Abstract: An LP gas carburetor adapted for use as the only carburetor for an engine or, alternatively, for use in conjunction with an existing gasoline carburetor (in particular, a two barrel carburetor) on an engine, the LP gas carburetor comprising a body adapted to be mounted on the engine, the body having two main passages and one auxiliary passage extending therethrough for the flow of an air-fuel mixture through the LP gas carburetor, a main inlet port in communication with the main passages for the flow of LP gas to the main passages, and an auxiliary inlet port in communication with the auxiliary passage for the flow of LP gas to the auxiliary passage. A main valve is provided for controlling the flow of LP gas from a source thereof through the main inlet port to the main passages, and an auxiliary valve is provided for controlling the flow of LP gas from the source through the auxiliary inlet port to the auxiliary passage for the idling of the engine.