An internal combustion engine (10) fitted with a carburetor (40) is provided with a fire-resistant cover member (62) having a front wall (65A) facing an air inlet port (44) of the carburetor, and a breather tube (60) having an inlet end (60A) connected to a crank chamber (28) of the internal combustion engine main body, and an outlet end (60B) supported by the cover member at a position located between the front wall and the carburetor.

An internal combustion engine (10) fitted with a carburetor (40) is provided with a fire-resistant cover member (62) having a front wall (65A) facing an air inlet port (44) of the carburetor, and a breather tube (60) having an inlet end (60A) connected to a crank chamber (28) of the internal combustion engine main body, and an outlet end (60B) supported by the cover member at a position located between the front wall and the carburetor.

An internal combustion engine (10) fitted with a carburetor (40) is provided with a fire-resistant cover member (62) having a front wall (65A) facing an air inlet port (44) of the carburetor, and a breather tube (60) having an inlet end (60A) connected to a crank chamber (28) of the internal combustion engine main body, and an outlet end (60B) supported by the cover member at a position located between the front wall and the carburetor.

An internal combustion engine (10) fitted with a carburetor (40) is provided with a fire-resistant cover member (62) having a front wall (65A) facing an air inlet port (44) of the carburetor, and a breather tube (60) having an inlet end (60A) connected to a crank chamber (28) of the internal combustion engine main body, and an outlet end (60B) supported by the cover member at a position located between the front wall and the carburetor.

A system of optimizing carburetor operation comprising: a carburetor controller; an air-fuel ratio sensor; a first communication channel; a processor; a power source; a non-transitory computer-readable memory element; a second communication channel for transmitting and receiving data; an external device; wherein said sensor sample air-fuel ratio in said carburetor; said sensor send said air-fuel ratio information via said first communication channel to said processor; said processor store it in said non-transitory computer-readable memory element; and said processor also send said information to said external device via said second communication channel. A carburetor spacer apparatus with multiple ports is also presented.

A system of optimizing carburetor operation comprising: a carburetor controller; an air-fuel ratio sensor; a first communication channel; a processor; a power source; a non-transitory computer-readable memory element; a second communication channel for transmitting and receiving data; an external device; wherein said sensor sample air-fuel ratio in said carburetor; said sensor send said air-fuel ratio information via said first communication channel to said processor; said processor store it in said non-transitory computer-readable memory element; and said processor also send said information to said external device via said second communication channel. A carburetor spacer apparatus with multiple ports is also presented.

A carburetor includes a passageway having a constricted section, a nozzle directed into the passageway proximate the constricted section, and a shaft having a surface that at least partially defines the constricted section. The nozzle is configured to deliver fuel to air passing through the passageway, and the surface includes a contour that is configured to be moved relative to the passageway to change the area of the passageway through the constricted section.

A carburetor includes a passageway having a constricted section, a nozzle directed into the passageway proximate the constricted section, and a shaft having a surface that at least partially defines the constricted section. The nozzle is configured to deliver fuel to air passing through the passageway, and the surface includes a contour that is configured to be moved relative to the passageway to change the area of the passageway through the constricted section.