That seems a little low. If I remember correctly, I was getting about those rpms with my last 21cc Kioritz, but with an APC 15x8 and at 4200' altitude and 90+ degrees. I don't remember now, did you gut the exhaust and provide two outlets of about 7/16" i.d., and install a larger carb?? My hopped up 23.6cc Kioritz turns a 16x8 at 8200 rpms here at this altitude. Pulls a 10.5 lb. plane straight up a long ways!

Amsoil is supposed to be good at 100 to 1, though several people have recommended running it at around 40:1. That's what I'm running right now. You probably won't notice any benefit with higher octane fuel, and might notice a decrease. These little engines just don't need it.

Good luck, and keep us posted,
AV8TOR