PURPOSE: To accommodate an exhaust pipe compactly within a limited space by connecting, in front of a crank case, the exhaust pipe to an expansion chamber of a silencer in a detachable manner.

CONSTITUTION: Since exhaust pipes 14 and 15 and a silencer 21 are connected together in front of a crank case 18, the space of this connection part can be opened widely both forward and sideward. As a result, the exhaust pipes 14 and 15 and the silencer 21 can be attached and detached easily, enhancing work efficiency. Looped parts 16 and 17 of the exhaust pipes 14 and 15 are located between both right and left down tubes 4 and 4, while they are bent within a plane nearly parallel to the front surface of an engine 13. With this contrivance, despite their elongated length, the exhaust pipes 14 and 15 can be accommodated compactly within a limited space without jutting out sideward from the frame of motorcyle.