I finally got around to running a Ryobi 31cc. It produces 7100 rpm iwth a 18x10 APC. CDI auto advance ignition. I used a bigger carb and I bent the reed valve stop a little. That seems to be pretty good for this engine. It looks like a good physical fit in my Balsa USA 1/4 Fokker D-7. BUSA recomends a Zenoah G-26 in that plane. It looks like the Ryobi is doing a little better than a G-26. Since I would have to use a bunch of nose weight with a G-26 might this engine be a good choice with a 20x6 prop?

I have some others like an EFCO 39cc, Zenoah 41cc, and a Homie. All of these have the carb and exhause out the side of the jug. That might make a messier installation than the slim Ryobi. Any comments on these types of engines for this plane?