Hello guys,
My plug is fouling very fast on my 300Ex , it has a 11.5 to 1 piston and a web cam in it. Is it the rings or a carb jetting problem? The motor has low hours on it.

 

Try using a hotter plug.

 

If it keeps fouling plugs you are rich or the carb is dirty. Do you have a pipe?? If you do and combined with the piston and pipe you should have around a 132 main and needle on the 4th notch down, and your air screw 2 turns out, if you have it jetted like that your pilot jet should be fine stock. Is your air-box stock?? if not you need to open it up a little and get a performance filter to take advantage of the cam and piston. I would not reccomend running stock exhaust if you are, if so you should run about a 125 main and clip in the middle. I always run NGK plugs, I don't believe in split fire they foul easy and are pretty expensive. Run a NGK D8ES, or even better DR8ES-L. Changing to a hotter plug isn't going to help the jetting much. Good luck and me what mods you have

 

My guess is its running too rich, unless the plug is oily.

 

Thanks Guys,
But I have another what if question. My son was racing the machine in a MX race and someone landed on the back of him damaging the disks on the White Bros E series pipe. I wonder if the damage to the pipe could cause some of this problem.
Thanks