250-500cc WR 250 Electrical issue!!

G'day all, got a 06 WR250 and my mate mig welded the expansion chamber mount back onto the frame for me and after about 1 hour of riding on Sunday, thought I'd done a plug (havnt ever done one before) and changed and kept going, another couple of Kays down the road same thng, lost power and stopped.. Another plug went in and started straight away again.. Now I was riding with 16 others so everyone had their reasons but the plugs where coming out looking as new. (so they should after a couple of kilometers). The bike ran ok as long as I kept the revs very low, but as soon was on the pipe it would stop again. So any ideas weather it could be the stator gone or the coil or something else, he used the foot peg as the earth and I cant see the stator dying, but I'm no mechanic!!

Could be a dodgy kill switch? Does it die or cough and splutter?

Pull and stator cover off and examine the stator itself, check for broken wires etc as the symptoms you describe sounds like the stator is on it's way out., you could connect the wires coming out of the stator and measure the ohms (download a manual).

check wires insulation melting etc sounds like electrical issue check for a fat regular spark.if it ran good before then the welding has damaged something.

Most of the time, welding won't hurt the stator, but it can hurt the CDI box ( or ECU ) and possible the coil. As suggested, meter the box and coil as per the shop manual and see how it comes out.

I didn't think it would hurt the stator but I'll drop it off to get it measured, it has never missed a beat before welding and was fine for about an hour into the ride.. It idled fine and ran well until about 1/3 rev range, a anymore and it lost all torque and ran weak (weak spark up high) but I'll do a top end while at at.. Cheers guys..