is the flywheel rusty?? inside or out? clean the little pads on the out side of the fly wheel where the pick up reads to fire the motor!
Do you have a ground going from the engine to the chassis?? is the frame painted or powder coated?? sand all the powder coast off of where the egine mounts go threw. ( I know it sounds dumb but I have seen it cause no fire!)
Did you replace the cdi and stator with known good parts?? have you ohmed the stator with a meter?? un plug it and read the stripped wires first, then the soild wires. they should be within 100 ohms of one another. ( example, one set is at 17 ohms, other set of wires is at 117 ohms. give or take a few) if you bypassed the key, did you reconnect the wires to one another? seen that one a few times too!
is the pick up on the stator set at .018-.020??
report back and we will go from there.