Patent ID: 7278629

Claim:
A carburetor having a main system for delivering main fuel to the venturi area of an air intake passage that passes through the carburetor main body, and a low-speed system for delivering low-speed fuel to the throttle valve area, wherein the low-speed fuel system comprises a flow rate control mechanism that is linked to a throttle valve and is capable of varying the low-speed fuel flow rate, and the flow rate control mechanism causes the low-speed fuel flow rate to increase as the throttle valve opens from the idle position until the point in time at which the main fuel begins to flow, and thereafter causes the low-speed fuel flow rate to decrease as the throttle opens to the maximum degree of opening and become substantially zero in the high-output region, wherein the flow rate control mechanism includes an on-off valve for opening and closing a low-speed fuel channel in the low-speed fuel system, wherein a valve element of the on-off valve increases the degree of opening of the on-off valve as the throttle valve opens from the idle position until the point in time at which the main fuel begins to flow, and thereafter decreases the degree of opening of the on-off valve as the throttle opens to the maximum degree of opening and until the on-off valve is substantially closed in the high-output region.