440ex-which spark plug

[440exnacsracer]

i just had a 440 kit put in my ex and it runs fine for a few hours, then the plug fouls. several people have told me to run a hotter plug. i have a k&n with airbox holes raised needle jet, and well you can see the rest below. what # plug do you 440ex'ers run? i was thinkin of a dpr9z or dpr10z. thanks for any tips.
Ben

[MIKE400EX]

Try a 165 main, needle clip in the 4th position (from the top), and probably a 42 pilot/slow jet. That should get you real close. With that piston, your true compression is probably around 9.5-9.8:1.
You might use the stock plug if it doesn't ping any. If it does, try the next colder plug - which is a DPR9Z. Note: The higher the number (with NGK) the COLDER the plug. What you really need to do is change the cam - otherwise you won't feel much of a difference at all.

[Dave400ex]

I was having Problems with mine Fouling and TC told me to run a D7EA because my Jetting was on and it hasn`t fouled since.