foul plug

Recently had 426 motor rebuilt, been running like a champ. It has about ten hours on it, all trail stuff. Started it up yesterday, ran choke for maybe a minute then turned it off, put gear on, restarted and headed down the road. Got couple hundred yards down the trail and the bike stalled as I was slowing. Couldn't get it restarted. Pushed back to the house changed plug and fired right up. Never touched the throttle while trying to restart. What could have caused the plug to foul under normal riding conditions?

I've heard shutting the motor off before it is fully warmed up can do that.

My WR426F has given me some real starting headaches, these are my basic rules to avoid problems:

-If I start it up, I make sure to let it get fully warmed up before shutting it off

-Always use fresh gas (I had some 3 year old stuff = bad news)

-Don't touch throttle while it's not running

Push starting works great if your in a bind and just want to get it running. Go through the standard startup procedure (kick starter till at top, pull decomp lever and kick starter down slightly) but instead of kicking it over at the end just get it rolling and pop the clutch in first. A slight downhill helps obviously.

Was the plug wet or black, clean it with a wire brush if its black or dry it over a gas flame for 20seconds the wire brush it, check gap should then be OK if not replace with a Iradium tip, should never have a problem again.

I had difficulty with fouled plugs constantly with my 00 426. I was running rich and would bog on the bottom. After many adjustment and needle changes the fuel/air mixture got better. The carbs are very tempramental. Until it was dialed in properly< i was fouling plugs with each ride. With a proper mixture this shouldn't happen. I only occasinally foul a plug. And, I find that this will typically happen when I don't let the bike get hot before killing it. Now... I won't crank it until I am ready to hit the track. This also seems to help.

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