G'day all

I recently bought a LEO 46 pretty cheaply on a certain auction site. I bought it as a challenge and to later convert to diesel as an experiment but in the mean time I have put it in a friend's plane to give a a bit of running. I am running a commercial fuel with 10% nitro, 5% castor, 15% synthetic and methanol. I think the plug is an OS A3 because I had several I got by accident. The prop is a Bolly "clubman" 11 x 5.

It started easily from new but it seems to have high compression and is easiest started by hand. The carby seems to me to be be very insensitive - large changes to the HS needle make very little difference and the LS needle is also a blunt instrument.

It flies the plane well but as the plane is overpowered (it is a Sig kit built LT25) it flies best on about half throttle. On full power, everything sounds fine, idle is reasonably stable for a new engine (has had about 20 minutes running now) but at mid range I suspect it is pre-igniting. Lots of crackily popping noises on top of the normal two stroke exhaust note.

I am considering adding an extra head washer and perhaps trying some lower nitro fuel but none is available where I am so I am open to other ideas, hints etc. And could the A3 be too hot and so causing pre-ignition?

Thanks in advance.

Mike