So did your motor eat the screw? Just maybe you can pull the head and get it out without doing much else. I'd try it and see how it goes. Pull the head to get a look see and if you can retrieve the screw. Even if there is some damage to the cylinder wall I think I'd bolt it back up and see how it runs if you can retrieve the screw. If you have to rebuild I personaly wouldn't go with a big bore kit. I don't think they are worth the money. You might have to rebore the cylinder if the wall is tore up and if that's the case you'll be buying a piston and ring set and top end gaskets. It's pretty easy to do a top end. You'r valves are probably OK.

Doug - Olympia - Washington
 I don't know how many CTs I have.