Just wanted to comment on your engine building post. I also am interested in a increased engine CC combo (naturally!). Your comments and questions parallel my experiences in the snowmobiling world. I spent years combining Polaris smallblock components in the same manner you are heading (boring/clearance case openings for larger cyls/pistons etc., matching ignition components, tuning). My favorite combo included a 440cc bottom end with overbored 600cc cylinders that accepted 700cc pistons! 135+HP. I can't wait to get my hands on some raw material! Best of luck.