Carburetor with second choke break

A staged carburetor for an internal combustion engine comprising;

• a carburetor body in which at least one pair of induction passages is formed for air to be drawn into said engine, said pair of induction passages including an inner induction passage having a venturi therewithin and an outer induction passage encircling said inner induction passage;
• a throttle valve positioned at the outlet of said pair of induction passages and movable between a closed and an open position to control the flow of air through said induction passages;
• at least one fuel circuit through which fuel is delivered from a source thereof to said inner induction passage, said fuel circuit having an outlet at said venturi;
• a fuel metering rod extending transversely of said induction passages and having a diameter variable along its length, one end of said metering rod being movable relative to said outlet to vary the quantity of fuel delivered;
• an air valve positioned in said outer induction passage and normally closing said passage whereby air is initially drawn into said engine only through said inner induction passage, an increased demand for air by said engine resulting in an opening force being exerted on said air valve to open it so air is drawn into said engine through both induction passages;
• means linking said air valve to said metering rod to move said metering rod relative to said fuel circuit outlet as said air valve opens thereby to change the quantity of fuel drawn into said inner induction passage, the quantity of fuel delivered to said inner induction passage at any one time mixing with the air flowing through said pair of induction passages at that time to produce an air-fuel mixture combusted in said engine;
• a choke valve positioned at the inlet of said inner induction passage and movable between an open and a closed position, said choke valve opening to a first open position when said engine is started;
• and
• means responsive to the vacuum created in said engine for exerting a force on said choke valve to move said choke valve from its first to a second and more fully open position, said vacuum responsive means including means for delaying application of said force for a period after said engine is started and said linking means including means for exerting the force produced by said vacuum responsive means on said choke valve and for moving said metering rod relative to said outlet thereby to vary the quantity of fuel delivered to said inner induction passage and produce a resultant air-fuel mixture whose air-fuel ratio is sufficient both to keep said engine running and reduce emissions produced by said engine.