What other engines can be swapped out in this bike? Mine is locked. Won't turn over. Can't turn it by hand with spark plugs out either. I got this bike for free. So, no money in it yet. Used FZ6R engines run about $450 on eBay. But, I'm thinking about making this a drag/street bike. Will a 1000cc engine fit? Or, do I have to stick with 600cc's?