I just tried running my 90SP on the Propower 10 fuel out in my backyard, and it seemed to throttle very fine. Transition was great and the fuel seemed to be ok. I only had one slight problem. I couldn't get it to idle below 1800 rpm without the glowdriver attached. Idle was adjusted so that it would just barely react when I removed the glowdriver. I could trim down the idle some, but then it would die on me as soon as I took a rapid transition from full bore and down to idle again. To keep the engine running I have to keep idle at 1800+.
Earlier I had this engine benchmounted and ran approx. 2 liters through it with a car-fuel i modified for use in the SP. I added some castor to the fuel i bought to get a blend of 70% methanol, 15,5% nitro, 9,7% synth.oil and 4,8% castor. With this blend and an APC 18x14 i could get it to idle below 1200 rpms for extended periods without any problems at all.
Lately I haven't been able to get hold of the fuel I used as a base for this blend, and in all honesty I prefer to buy the fuel ready made. I have also rotaded the cylinder to get it ideally positioned in the plane. I remember that when I did this the ports didn't match up equally much in the intake and exhaust as the manual says it should, but I can't remember wich port I let show the most. If it's one tooth wrong on the timing, could it cause this much difference, especially with the different fuel? Oh, BTW I now run a 18x12 Master Airscrew prop on the engine.