i have a 05 yfz 450. i just bought a pro circuit t-4 pipe and i was wondering what size jet i should run??? i live at 3500. i was thinking about putting a few holes in the air box or taking it off all together? any help woud be great.
thanks

 

Pull the lid go 165 main rip it up yer good.
Shady

 

thank you! what about the pilot jet or the needle?

 

If you remove the lid, try a 168-170 main, clip on 5th position, 45 pilot, play around with the fuel screw.