i'm not aware of any restrictions on motorcycle sizes for new riders anywhere in the US(i may be wrong though..) and 2 strokes are almost illegal beyond the little 49cc mopeds.

incidentally Indiana is about to start requiring the 49cc scooter riders to have a special license/permit to ride them. http://www.in.gov/bmv/3220.htm this is the result of various accidents involving scooters. (not to mention the 150cc ones are hard to tell from the 49cc ones at a glance)