I need help on what size jet to use. The pipe I bought is the White Brothers E series, K&n air filter and Jet Kit. With the stage one the jet they tell you to use is smaller then the stock Jet. So I will be using the stage 2, K&N says if you are below 3000 feet use the 170 if you are 3000 to 6000 feet use a 165jet and 160 if you are above 6000 feet.On the dyno jet needle K&N says groove #3 below 5000 feet or groove 2 above 5000 feet. This is a stupid question are they talking above or below sea level? I live in New Jersey which is at sea level, so what jet should I use. They also state to remove the air box lid on the stage two jetting. On my 300ex I had the same set up but used and FMF power core pipe and never removed the lid, I never had a problem. Thanks for the help.

 

From the info that you have provided, I'd say that they want you to run the 170 main and put the needle clip on groove #2 with no airbox lid. If you want to retain the airbox lid then I would suggest using the 165. Every engine is different and only trial and error will give you the perfect jetting combo.

 

Keep in mind, the main jet sizes on Kehin (400EX stock) jets are NOT on the same "scale" as the main jets in DynoJet Kits from K&N. And due to the needle taper being different on the K&N Jet kit, a 150 K&N main jet WILL flow more gas than a 150 Kehin Main Jet, using the stock needle.

If you dont want to mess with the airbox, go with Stage 1.

OR go with the Stage 2 recommendations, and either run without an airbox lid, or do like I did and put a 6-inch port in the box lid. I would not touch the needle, and stay at or below a 160 K&N main jet.