Fouling plugs ?

I have 2011 YZ450F and fouling plug bot every 4 rides ? I had an unplugged air sensor thought that was my prob. Guess not ! I have the MXA performance map loaded. Runs great but will foul plug @ first cold start.? Plug really black. Thinking maybe valve seals r leaking some. Wondering if anyone has this happen ???

It sounds like you may have the incorrect spark plug.  One heat range too cold will do this.


Of course, it could also be weak ignition or a rich condition.

Stock plug and did same w/ stock map.??

 A rich condition could be the result of a leaking or otherwise faulty injector, or an incorrect PM signal from the ECU.  Could also be the ignition, as I mentioned. 

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