I agree with Charlie. I have a pair of 90 size pattern planes, both with upside-down mounted OS 1.20 AX engines. They can be a bit of a pain to prime, but I learned to put my finger over the exhaust and prime it that way. But, properly tuned, just as any other glow engine, it should start and run just fine.

I did NOT have the same luck with the Evolution 1.00NX engine. That's what pushed me to the OS engines... which, once broken in and tuned right were.... are just fine.

CGr.