what size jets should i use for a 400ex with a pro circuit slip on? Pro circuit told me i didn't need to re-jet but i've already fouled out a plug.

01 400ex(yellow)
Pro circuit pipe
AC Pro pegs
renthals

 

yea the same thing happened to me to whenever i got my pc pipe. it ran fine for a while until one cold morning i tryed to start it and the plug was fouled. supposably 170 is ur right main jet but i run a 160 in mine and it runs perfect.

 

I use a 155 main jet with the Pro Circuit pipe and no airbox mods and my jetting is spot on during normal riding weather (55 to 80 degrees). Hope this helps.