ATC 250R Wont stay Running

[1986ATC250R]

So I have a 1986 ATC 250R that will startup (sometime), run fine for about 30 seconds then die. Once it dies it is a pain in the ass to get going again, and once it does the same symptoms occur. I put fresh fuel in it 32:1, completely gone through the carb but the same symptoms occur of it running for about 30 seconds then dying. I have owned the bike for several years know and it has always run fine before. Also, I have always run a NGK B9EGV spark plug in it because the bike would not have a crisp power band with the BR9ES the Manuel calls for. I am beginning to think I have an ignition problem because I cannot really see (confirm) spark when I put the plug against the head. Any advice/experience would be great thanks ???????? Also the bike is completely stock, as far as I know except a full fmf exhaust, K&N air cleaner and some drilled holes in the airbox.

[crev]

I had close to the same problem. mine turned out to be bad crank seals. hope you have better luck then I did

[crev]

When is the last time the bottom end was gone through.

[1986ATC250R]

Not Sure, not in the 2 years I have owned it. You guys don't think electrical ???

[atc007]

I personally despise the G plugs. But if you're bike likes them. Can't argue. Other than doing a leak down test,,,right way to do it,,,simply pull your mag cover and see if there's wet sewage around your stator. Get it running again, at idle, spray starting fluid all around the crank seal, cases,intake boot etc. If it's sucking air. She will rev to the moon. If not an air leak. Most likely ignition. You are sure your petcock is flowing perfect??,no foreign objects in your tank to clog the flow?