Fuel tank for vehicles

A fuel tank comprises a main holding body (2) containing a predetermined amount of fuel, a secondary holding body (3) hydraulically connected to the main holding body (2) and adapted to be hydraulically connected to the carburator, and transfer means (8) operatively active between the main (2) and secondary (3) holding bodies to move fuel from one body to the other; the secondary holding body (3) defines a compensation chamber (3a) designed, under operating conditions, to keep an operating level (3b) of the fuel at least as high as a positioning height of the feeding and mixing device.