For over a month now, my 400EX just doesn't want to run. Last year the cold weather never affected it, but this year is obviously different. The only way I can get it started is if I put in a brand new spark plug in every time I want to start it. Do you think it is related to the pilot. I'm still running the stock pilot. The only thing I've really done lately is the Wiseco prolite piston with the 10.5 to 1 compression, but it has ran for better than 2 months since then without any problems. Sorry about the long post, I'm retarded
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I had the same problem with my 400ex when it sat for a couple weeks without running. The dealer told me that they were bad about fouling up spark plugs. You need to adjust your carb to fix the problem. If you can't get anywhere, then call the dealer. They are usually pretty good with that crap.