well,I tell ya what.....I would bet you've got any where from a 21cc to a 26cc most likly closer to 21cc. Take a look at the piston through the exhaust port and see if it has two rings. The higher quality one's do. Then start with a Zinger 16x8 and tach it. Keep the engine somewhere in the mid 7000 rpm range, going larger in prop pitch like to a 16x10 if needed. strap it to the blunt end of a plane and see what it does. 1/4 scale lightplane like a Super Cub from hanger 9 could be flown with very good performance on your engine most likely. Isnt experimenting fun?...lol....I bet you got a flyable engine, sometime the hard part is mounting it to a plane. Put up some pics and maybe someone has your engine that can help. Piper