400ex carb jetting ?

[bdrue]

i have a 2004 400ex. i pu on a uni air filter along with a curtis sparks advance key. i know im running lean, what jetting changes should i make? thanx

[400Ex_Rida]

try a 150 or 155 main jet. How do you like the sparks advance key, I ordered mine yesterday.

[bdrue]

i havent rode it since i installed it, because its backfiring, thanx for the

[bdrue]

i havent rode it since i installed it, because its backfiring, thanx for the

[bdrue]

i thought the main jet controlled the 3/4 to full throttle only?

[bdrue]

i thought the main jet controlled the 3/4 to full throttle only?

[Colby@C&DRacing]

put a 42 pilot in it ans a 155 main jet:)

[cals400ex]

Originally posted by bdrue
i thought the main jet controlled the 3/4 to full throttle only?

this is what the main controls. i have a feeling your not bad on the main, but the fuel skrew is probally a little lean. yes, you can put in a 42 pilot or just try to turn the fuel skrew out some. just don't go past 3.5 turns out or so. if your still lean at idle when your at 3.5 turns out, you definately need a larger pilot. if it is popping on deceleration, i bet your just a little lean on the pilot or needle. from my experience with jetting (this is around sea level), i would not go bigger on the main than a 150. i run a 155 main jet in the hot months on my built 406. however, i jet to where i get the most performance. some people jet a little rich so their bikes run cooler. this also hurts performance a little too. there is enough difference between a 150 and 155 for example to determine who will win in a race up to top speed between my friend and myself. i think you will be killing your upper gear performance by going bigger than a 150. elevation and temp play a big role here though. bye the way, i assume your stock besides the key and filter?? everyone has their own perferences, but i know what will give me the best performance down where i live. good luck