To optimize fuel supply of an engine with a carburetor during engine operation, a throttle opening degree detection sensor detecting a throttle opening degree and a control unit controlling a valve body variably controlling an opening degree of a fuel discharge part or a fuel supply passage based on a map are included. The map includes a plurality of sections divided based on the throttle opening degree and an opening degree of the valve body set for each section. The opening degree of the valve body set for each section is the opening degree of the valve body at which the engine rotation speed is highest in each section. The control unit controls an electric actuator driving the valve body to achieve the opening degree of the valve body set in a section to which the throttle opening degree detected by the throttle opening degree detection sensor belongs out of the plurality of sections.

To improve responsiveness of fuel supply control, a rotary carburetor 100 has a nozzle 8 including a fuel discharge port 8a and a needle 10 disposed coaxially with the nozzle 8 and disposed with a portion inserted into the nozzle 8. The needle 10 can be displaced relative to the nozzle 8 to change an effective area of the fuel discharge port 8a. The rotary carburetor 100 has an electric motor 14 for displacing the needle 10 along an axis, and a drive mechanism component 12 interposed between the electric motor 14 and the needle 10 and converting a rotational movement of the electric motor into a linear movement.

A carburetor includes a body with an air intake path, a fuel pump and a fuel pressure regulator. The fuel pump and fuel pressure regulator are positioned on the same side of the body. A fuel pump and metering chamber diaphragm is sandwiched between the body of the carburetor and a pump body and cover. The diaphragm separates a pump chamber from a pulse chamber of the fuel pump and separates a fuel chamber from an air chamber in the fuel pressure regulator. Inlet and outlet flapper valves are part of the diaphragm or a separate flapper valve member positioned between the body and the diaphragm.

A carburetor includes a body with an air intake path, a fuel pump and a fuel pressure regulator and having a main fuel jet and nozzle assembly with a main fuel jet releasably coupled to the body of the carburetor. Alternatively, a main fuel jet and nozzle assembly includes a nozzle and check valve retainer formed as a single component. In other embodiments, a carburetor is provided having a fuel pump and fuel pressure regulator positioned on the same side of the body. A fuel pump and metering chamber diaphragm sandwiched between the body of the carburetor and a pump body and cover, separates a pump chamber from a pulse chamber of the fuel pump and separates a fuel chamber from an air chamber in the fuel pressure regulator.

An engine that includes an air intake, a combustion chamber, an air passageway that is configured to channel air from the air intake toward the combustion chamber, a carburetor, a throttle plate, and a fuel atomizer. The carburetor includes a fuel bowl with a fuel well, a carburetor passageway that is fluidly coupled to the air passageway and configured to channel air and fuel to the combustion chamber, and a carburetor nozzle that has an inlet configured to receive fuel from the fuel well and an outlet disposed proximate to a constricted section of the carburetor passageway. The throttle plate is disposed downstream of the carburetor nozzle, and the fuel atomizer is configured to provide fuel to the carburetor passageway.