Hey fella's
Have you guys ever installed one of these? How do these work better than stock? What power gains should I expect? I just put on a K&N Air Filter and outerwear (removed box lid), and a White Bro's E slip on- (this rocks!). I've seen a pretty good power gain so-far.

Also- can someone explain to me what these "jets" do?.. and what the number (size) means? I keep seeing posts about changing the size... what number is stock? how does changing the size affect performance?

Thanks for your help!

 

It not worth the 140 bucks they run at a shop. The bigger the number the more gas it flows into the carb.

 

RotGut...I agree with dirt save your money. You can buy jets for $4 or so. It's a marketing scam.

 

I have a K&N jet kit I am running a 155 main jet with K&N, supertrapp exhaust, 3 inch hole in airbox lid. The stock jet in the 2000 400ex is a 148, you should be running about a 155 or 160 which comes in the kit. It is very easy to change the jet. Turn off the gas, on the bottom of the carb there is a bolt take that out, careful a little gas will come out, then feel up inside there and what you feel is the jet, then unscrew that and put in the dynojet.