Hi all,</p>

Thanks for the input so far.</p>

I checked and the plug cap is tight and secure. The engine is an Evolution 35cc with the plug that came with the engine. I have no idea if this is the resistor type or not but would this not be the type supplied by the engine manufacture given the fact it is an engine made specifically for model use? How can I tell if it is a resistor type?</p>

Nothing else changed apart from the two batteries, still in the same location but of a larger capacity.</p>

The entire model was built by me from new items, engine, servos, etc and has only had a few flights while on 35MHz. No damage to any shielding, servo leads, servos, etc.

I am using a Spektrum AR7000 receiver, JR 12x Tx, upgraded switches, HiTec servos.</p>

I know I am missing something, but have no experiance with petrol engines.</p>

Please keep the suggestions comming.</p>