Review of the K&N filter and Jet Kit for the 400EX
(written by Duner400ex)

I did a review on the Yosimura pipe and noticed that it had alot of torque to it. I nocited that when i tryed to take off in 1st i would have to give it alittle more throttle. Once you kicked it up into 2nd the 400ex started pulling very hard. There was one thing that wasn't right, there was a miss at the begining of each gear. I knew i needed to get it rejetted, but i had no idea what rejetting the carb and putting on a K&N highflow air filter could do.

I bought a K&N Highflow Air Filter and Jet Kit from Rocky Mountain ATV for $44.99. When the accessories came in i immediately put on the the Highflow Air Filter. I warmed it up and took it out into the snow and didn't notice anything. I was very dissatisfied with the air filter. Then i thought maybe the jet kit and the air filter would work better. So i had my mechanic put in on.

When i got it back the 400ex rocked. No more having trouble getting into 1st and no more misses in each gear before it took off. The Jet Kit said it would improve throttle responce, torque, and up to 15% in horsepower. I noticed each and everyone of those. The one i noticed the most was the torque. The torque from this jet kit was amazing it was so fast i couldn't believe that $50.00 dollars worth could improve the 400ex so much. Now when i want to race i actually have a chance of winning off the line. I would definetly recommend to anyone who wants torque for a cheap price.