Thanks everyone for your tips and advice. I have read Tony Clarks article on using the 2 cell Lipo. If I'd read it before I started using the RCXL's, I might have just stuck with Zenoah's ignition. I been using the same ignition on a G20 with no issues.

I'm pretty sure I had the plug cap on completely. It is difficult and I have to push down hard on the engine to seat the cap. I will take another look.

Have to admit this is the most baffling engine problem I've encountered. Once it's solved I'll post the problem again and the solution.

Any other suggestions would be welcomed.

Regards