Sometimes it's the most dumb thing... plugging the battery in backwards will cause no contact, kill switch ot installed correctly, switch installed backwards.

Slow down and become methodical... eliminate evrything but the battery (use a 4-5 cell nicad/nimh to test... no reg) and plug it in direct to the ignition.

I once spent an hour trying to find a "problem" with the engine... later found it was just I pkugged the Hitec battery connector into a Futaba switch jack backwards... no juice. No spark...

As I said... sometimes it's the simpest things that get us.