whats the best jetting for a kfx 400 with a yoshimura exaust and a k&n filter with no lid at sealevel

 

Best to let the professionals decide what is best. Years back I had a Praire and needed a rebuild kit, called the folks at "Uni" and explained all the machine had on it and they sent me the proper kit with detailed instructions. Installed the kit and it worked perfect, plug came out the right color, only needed to make minor adjustment to idle mix screw. My machine's performance increased noticeably.

 

This is still a good guide on stock jetting plus the jet kit has enough jets and instructions on jetting when using after market exhausts,air filters,modified air boxes,air box lids removed,etc.https://www.jetsrus.com/a_jet_kit_at..._2003-2006.htm

 

Have you find the correct jetting?

I have a 440 kfx 2003 with a Yoshimura exhaust and I do no what to do with de carb