I have come across the rear end of a drive shaft bike but dont know any more about it than that.  I have attached some pictures and I hope some one can help me ID it.  Thanks in advance.

 I don't have an answer for you but I think you're right with the BMW guess ... you might want to try asking over here: http://i-bmw.com/

Dont be surprised if it happens to be the rear swing arm etc to have come from a twist and go scooty thing...lol...Brakes dont look big enough for a Beemer