To prevent the escape of fuel inside a float chamber for an engine to the outside by way of a starter when the engine is being carried.

A cylinder bore 10 of an accelerator is situated above a main nozzle 9 in the longitudinal axis line M1-M1 thereof, on the line Y-Y which crosses over the center M1 of the main nozzle 9 and is perpendicular to the longitudinal axis line X-X of an intake passage 2, and on one J side of the longitudinal axis line X-X. The upstream end 11A of a fuel lead passage 11 communicating with the cylinder bore 10 is made to open into a float chamber situated on the downstream K side of the line Y-Y as well as on the other H side of the longitudinal axis line X-X.