I bought an 01 YZ 426 a couple of months ago, and it has started to foul plugs rapidly. The bike runs great when it runs, but as soon as I stop it won't kick back up again. The other day I took it out and rode for about two solid hours. After taking a break the bike wouldn't start, and the obvious answer was a fouled plug. I did a field cleaning because I didn't have a spare (I didn't have the spark plug wrench needed either, but thats it another story and a lesson learned). I put the plug back in, and it kicked on the third try. I let it run for maybe five minutes or so and it fouled out again. I had changed the fuel, oil and cleaned the carb prior to this happening. So what could be making my bike foul out so easily?