If you aren't seeing the other mounting option, odds are someone on the team you got it from has cut it off already. (The motors are supposed to have a stud on the face plate, to which a belt tensioner attaches. You could remove the tensioner and retain the stud.) Clamping is a pretty good option, though unfortunately, I don't think these motors had an alignment boss around the shaft.
Basic specifications are
here (on page 8).
(For those who don't know, the mini-bike CIM was used on a Fisher-Price toy motorcycle, and provided in the 2006 and 2007 kits as FP801-005.)