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.

An adjustment device for a carburetor adjustment valve includes a limit cap and a sleeve to prevent over-operation and destruction. The limit cap having first and second projecting parts formed in the insertion hole. The first projecting part engages a first groove on the shaft part of the adjustment valve to hold the limit cap in a first position where the limit cap and adjustment valve rotate freely relative to the sleeve. The second projecting part holds the limit cap in a second position pushed in from the first position where the adjustment valve having a limited range of rotation. The limit cap has an outer circumferential locking part formed on the outer circumference and the sleeve has an inner circumferential locking part formed on its inner circumference. In the second position, the inner circumferential locking part locks the outer circumferential locking part and prevents rotation of the limit cap.

An adjustment device for a carburetor adjustment valve includes a limit cap and a sleeve to prevent over-operation and destruction. The limit cap having first and second projecting parts formed in the insertion hole. The first projecting part engages a first groove on the shaft part of the adjustment valve to hold the limit cap in a first position where the limit cap and adjustment valve rotate freely relative to the sleeve. The second projecting part holds the limit cap in a second position pushed in from the first position where the adjustment valve having a limited range of rotation. The limit cap has an outer circumferential locking part formed on the outer circumference and the sleeve has an inner circumferential locking part formed on its inner circumference. In the second position, the inner circumferential locking part locks the outer circumferential locking part and prevents rotation of the limit cap.

A carburetor for a two-stroke internal combustion engine whereby airtightness is maintained and intake of uncombusted fuel into an air path is prevented. The carburetor includes a circular cylindrical valve hole and a rotary valve fitted into the valve hole such that it can rotate and is disposed perpendicularly across a fuel intake path and an air intake path which are formed substantially parallel with respect to each other, and a fuel supply-side bore which controls the flow rate along the fuel intake path and the air supply-side bore which controls the air capacity along the air path pass through part of the cylindrical portion perpendicularly to the axial direction of the rotary valve, and annular recesses formed in part of a circumferential wall of an outer circumference of the rotary valve so as not to correspond to at least the fuel supply-side bore and the air supply-side bore.

A carburetor for a two-stroke internal combustion engine whereby airtightness is maintained and intake of uncombusted fuel into an air path is prevented. The carburetor includes a circular cylindrical valve hole and a rotary valve fitted into the valve hole such that it can rotate and is disposed perpendicularly across a fuel intake path and an air intake path which are formed substantially parallel with respect to each other, and a fuel supply-side bore which controls the flow rate along the fuel intake path and the air supply-side bore which controls the air capacity along the air path pass through part of the cylindrical portion perpendicularly to the axial direction of the rotary valve, and annular recesses formed in part of a circumferential wall of an outer circumference of the rotary valve so as not to correspond to at least the fuel supply-side bore and the air supply-side bore.

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.

In at least some implementations, a charge forming device includes a body defining at least part of a first passage, a throttle valve movable relative to the first passage between an idle position and a wide open position, an air bleed passage communicated with the first passage, and a control valve. The control valve may be arranged in the air bleed passage to selectively inhibit or prevent air flow to the first passage from the air bleed passage. And the control valve is moveable between a first position and a second position in response to movement of the throttle valve wherein greater air flow is permitted from the air bleed passage to the first passage in the body when the control valve is in the second position than when the control valve is in the first position.

In at least some implementations, a charge forming device includes a body defining at least part of a first passage, a throttle valve movable relative to the first passage between an idle position and a wide open position, an air bleed passage communicated with the first passage, and a control valve. The control valve may be arranged in the air bleed passage to selectively inhibit or prevent air flow to the first passage from the air bleed passage. And the control valve is moveable between a first position and a second position in response to movement of the throttle valve wherein greater air flow is permitted from the air bleed passage to the first passage in the body when the control valve is in the second position than when the control valve is in the first position.

A carburetor with a fuel adjustment tamperproof valve assembly and specialized tools for adjusting the valve assembly. A needle valve is received in a recess in a carburetor body with a passage open to the exterior of the body and a cylindrical surface of the passage. A valve head with a cylindrical exterior surface is received in the passage with a slight clearance between them. The specialized tools are engageable with the head to adjust the valve by rotating it.

A carburetor with a fuel adjustment tamperproof valve assembly and specialized tools for adjusting the valve assembly. A needle valve is received in a recess in a carburetor body with a passage open to the exterior of the body and a cylindrical surface of the passage. A valve head with a cylindrical exterior surface is received in the passage with a slight clearance between them. The specialized tools are engageable with the head to adjust the valve by rotating it.