Ok, it's been a little over two years since I started this project and it's finally finished.... 25cc engine from John M. and a Sig Rascal 110 is a GREAT combo. What I did was strip the engine down to nothing but the engine and the magneto, installed a Zenoah G-26 carb adapter, G-26 header pipe, found a Zama 10mm carb on a poulan 41cc chainsaw engine and slapped a Zenoah G-26 velocity stack on it. Made a prop hub out of 1 1/4" aluminum round stock and threaded it to spin on the crank, installed a stud in the prob hub and made a washer from the same material as the prop hub. Drum roll please.............. 9250 rpm with a 16/8 Zinger prop. I would put a muffler on it if there were noise restrictions at my field but since there isn't MAKE IT LOUD. Hand starts great with some thumb choking to prime it. Let me tell you, this little engine is more than I need to fly this Rascal but you can NEVER overpower a plane. I fly around at 1/3 throttle and when I go WOT it tries to climb I'm attempting an electronic ignition version, the Zenoah EI system uses the same dimensions on the rear of the engine but I need to find a G-26EI to measure and make certain. the great thing is I still have 2 more engines to tinker with. Thanks everyone for the info, couldn't have done it without this thread.