Carburetors

Claim 1

An air valve carburetor comprising an induction passage, a throttle valve in said induction passage, an air valve upstream of the throttle valve, the air valve co-operating with the wall of the induction passage to define a throat of variable area and being controlled by the depression established in a mixing chamber which comprises that part of the induction passage between the throttle valve and the air valve in order to maintain that depression substantially constant during opening and closing of the air valve, a constant level fuel chamber for containing fuel to be supplied to the mixing chamber, a passage for connecting a space in the fuel chamber above the fuel level to atmosphere through a restricted vent and to a source of suction through a flow restricting device, means responsive to atmospheric pressure for controlling the relative flow capacity of said restricted vent and said flow restricting device, and a valve associated with the throttle valve, said valve being arranged to open an unrestricted vent which provides a connection of said space to atmosphere separate from the restricted vent when the throttle valve is moved to the closed position, wherein said means responsive to atmospheric pressure are arranged to control simultaneously the flow capacity of both said restricted vent and said flow restricting device, the respective degree of variation being such that the relative flow capacity is changed thereby.