an improved carburetor arrangement comprises a low - capacity fuel / air regulator for efficiently vaporizing rich mixtures of fuel and delivering them to a heat exchange vaporizer for heating and completely vaporized the rich mixture prior to delivery to an engine intake . an existing conventional fuel atomization system is eliminated and replaced with main combustion air gallery . the air gallery forms a low pressure for drawing heated rich mixture from the vaporizer and subsequently mixing it with a larger amount of incoming fresh air from the gallery for forming a stoichiometric mixture . preferably the mixture is passed through a mixing chamber before delivery to the engine intake . preferably the fuel / air regulator is a low - capacity carburetor , such as that used for motorcycles , snowmobiles and the like .