[d_dionne8]

i have a 2005 crf 250 x and i had just bought an fmf pipe for it { ti powercore} and was wondering if i had to jet it. if so what size to jet it, i allready have a uni air filter on it and what other ways can i make it perform to its best.and is it better for the bike if i get the header

[Halen]

I have the same bike... with the same pipe.
Don't bother with the header. Spend the $65 and get the JD kit, open up the air box and run a 45 pilot with the 162 main and your bike will be like a whole new machine.
The JD kit comes with instructions on how to mod the air box, how to install the supplied O-ring for the AP, and a needle to change while you are there.
Total mods should take the better part of the day but WELL worth it.
Halen

[KevinM]

Ditto.. same bike.. I'm using the 42 pilot. Getting good results as well. Specs for my bike are below.

[d_dionne8]

thanks