PURPOSE: To shorten the width of an engine by directing the driving shaft of a fuel pump to the up-and-down direction so as to be perpendicular to the crankshaft, and by installing the fuel pump body on the crankcase, so that the projection of the fuel pump toward the engine side can be eliminated.

CONSTITUTION: A fuel pump 31 for forcedly feeding fuel both to a combustion- chamber fuel injection injector 8 and to an intake pipe fuel injection injector 14 via a fuel hose 32 is fixed to a crankcase cover 22 on the upper right side of the crankcase 2, and in the position nearly above a main shaft 15. In this case, the driving shaft 40 of the fuel pump 31 is directed nearly to the up-and- down direction so as to be perpendicular to a crankshaft 9, and is connected to a pump main shaft 21 via a connecting shaft 41 that has been journaled on the crankcase 2. And, the connecting shaft 41 is arranged on the same axis as the driving shaft 40, and the worm gear 41a provided at the lower end thereof is engaged with the worm 26 of the pump main shaft 21, so that it can be turned by the power of the crankshaft 9 that has been transmitted to the pump main shaft 21 via a reduction large gear 16 and a driving gear 25.