To obtain excellent accessibility and make a compact layout form possible by making a fixing screw radially oriented to a crankshaft, effective between a receiving part and a flange.

A plurality of receiving parts 17 are arranged around a second wall section 16, and a flange 10 is put on the receiving parts 17. Each receiving part 17 has a threaded hole 18, and a fixing screw 19 for tightening the flange 10 to the receiving part 17 is screwed into the threaded hole 18, that is, the threaded hole 18 and the fixing screw 19 are oriented toward a crankshaft 5 in a radial direction. The fixing screw 19 has a threaded pin 21 piercing a hole 20 in the flange 10, and a screw head 22. In this case, a starter rim 23 is fixed to the flange 10 between the screw head 22 and a crankcase 4. The flange 10 is elastically formed in a radial direction Ra in a fixing range 24 of the fixing screw 19.