Abstract: A carburetor of the type admitting simultaneous control of both air and fuel supply. The air supply is regulated by means of a linearly movable aperture means, whereas the fuel supply is regulated by means of a linearly movable rod means provided with groove means having a transverse profile of monotonically varying area. A selectable portion of said groove means can be coupled into a fuel conduit, thus regulating its effective size and thereby the fuel supply by means of a linear movement of said rod means. Said rod means and said aperture means are coupled for mutually proportional linear movement, thus accomplishing the simultaneous control. By appropriate manufacturing of the groove means it is possible to obtain improved fuel-to-air ratio for settings between idling and full gas. The rod means also works as a plunger in a cylinder, thereby rendering an accelerator pump function.