My bike in 4th gear has a ratio of 4.36:1, about the same as a stock 44 tooth. 25mph is a good speed for that gear so I would guess that the motor is turning about 5500 rpm. Again I don't have a tack but I bet it is a pretty good guess. When you get yours let me know the rpm you are at using a 44t and 25mph.
Motorcycle? Depends on the laws I guess. You can check my bike out here.
Looks like a motorized bike to me.