Variable venturi carburetor

A variable venturi carburetor comprising a fuel reservoir, a through passage-way mixture conduit (10), a throttle plate (12) swingably disposed for opening and closing the outlet end of said mixture conduit (10) and thereby metering the amount of mixture that exits from said mixture conduit (10), said mixture conduit (10) formed with a fixed venturi (14) upstream of said throttle plate (12), a vacuum sustaining plate (16) swingably disposed for opening and closing the throat of said fixed venturi (14) for controlling admission of air and for generating venturi effects in said mixture conduit (10) that are variable with the swingable positions of said vacuum sustaining plate (16), a first fuel nozzle (22) opening into said mixture conduit (10) at a point on one side of said fixed venturi (14) and on the downstream side of said vacuum sustaining plate (16), said first fuel nozzle connected through a fuel conduit (24) to said fuel reservoir, an opening sensor (40) associated with said vacuum sustaining plate (16) for sensing the opening of the throat of said fixed venturi (14), a control circuit (42) associated with said opening sensor for providing a drive pulse signal with its duty factor varying in accordance with the degree of opening of said vacuum sustaining plate (16) but held at a level when the degree of opening of said vacuum sustaining plate (16) is over a predetermined level, an electromagnetic valve (44) provided for opening and closing said fuel conduit (24) so as to control the amount of fuel drawn from said first fuel nozzle (22) in response to the drive pulse signal applied thereto from said control circuit (42), a second fuel nozzle (30) connected to said reservoir and opening into said mixture conduit (10) at a point on the opposite side of said fixed venturi (14) and on the upstream side of said vacuum sustaining plate (16).