I have a 2001 WR426 that I've had for a few years. When I first got it, the carb was gunked up so I replaced the pilot jet and disassembled the carb and cleaned it and since I've kept the carb very clean. It runs like a raped ape, and has been great for years. Starts on first kick, hot or cold. Idles like a sewing machine! This year I have a new problem that I'm not sure about. When it's idling, I hear it cutting out, almost like someone is pressing the kill switch. It has never done this before. The cut outs start after it gets warmed up a bit. I don't seem to notice them until it's been running for a minute or two?
It doesn't sound like jetting, and I have a adjustable fuel screw that I've gotten pretty good with. It almost sounds "electronic", like the spark plug is being shorted momentarily? At anything above idle, I have NO problem at all...still runs very strong with no cut outs at all. Just sitting at absolute idle is when these cut outs happen. They only last for a second. It will die also, occasionally, if the cut out is long enough at idle. Strange thing is this started after I washed it the first time a week ago. It's been several days, and I always start the bike and "heat it up" after i wash it to get rid of moisture. I've washed it and ridden mud hundreds of times with no problem before.
But it's still cutting out today after it's completely dry. I guess I'll replace the plug and I may pull the pilot out and see if it's gunked up. I may take the carb apart again. I did remove the coil and sanded the contact area on the coil and frame to make sure the ground was good. But the cut out sure sounds like someone hitting the kill switch for a second. Could my coil or CDI being going bad? Any other ideas? Gray, are you out there?