PURPOSE: To maintain slim outer view of the body, reduce the cost and improve assembling workability by arranging the air cleaner in its dead space in an air cleaner in a motor cylinder.

CONSTITUTION: A pair of cross pipes 17, 18 are installed on a main pipe 3 at a lower part extending to left and right, and the cross pipe 17 provides a recessed part which is formed at its upper in the longitudinal direction. An air cleaner 12 makes use of a pair of said cross pipes 17, 18 as mounting stays, a pair of hook members 19, 20 which can be engaged with the cross pipe 17 for mounting are provided at the bottom part, and a fixing part 21 which is to be fixed by fixing means, such as screws, etc. is provided on the cross pipe 18. A cone tube 26 has a quasitruncated cone shape, and the both end parts are respectively inserted to the air cleaner 12, and to a resonance chamber 11.