I just bought a 2002 400ex and am looking for a little more low end. Which pipe do you 400ex owners prefer and what jetting are you running? Also, if I took of the air box would it be better to go with a K & N filter and filter outwear or just filter and air box outwear? Thanks

 

Mikey

I put a Pro Circuit T-4 slip on pipe on my 2001 400. I got it from Rocky Mountain for $189. I really was impressed with the quality build of the pipe, the sound, and the power gain. I installed the pipe and a 155 main jet and got impressive gains in the mid and top end. The bottom improved some, but not as much as I want. I am slowly working on dialing the low end jetting in. I have put two 1 inch uni filter vents in the lid as of now. I plan on installing the remaining 4 in the spring and rejetting the pilot jet. As for the air filter, I am still running stock. I ride in really dusty conditions and I am not convinced the K&N does as good of a job filtering as the foam filters. Other people swear by them, so the choice is yours.