350x with 400ex carb tuning

[ATC350X 85]

I just got another 350x with a 400ex carb on it. The previous owner said that i should jet it down 10 numbers on the main jet. I know its definitely running rich, the plug has lots of carbon on it. He also has a K&N filter on it from a 400ex. Can I just lean out the mixture instead of rejetting? Does anyone know the stock jet size for a 400ex? I also want to get rid of the K&N, i think theyre more trouble than theyre worth. I have the original 350x carb but i like the accelerator pump feature of the 400 carb.

[HemiChallenger71]

If you lean it out on the air screw you will toast your motor. You have to pull that carb off and re jet it. It's not very hard. Go buy a book on it, or read up at dirt wheels or maybe someone can help you with the re-jetting, because it's easier to see pictures. Some carb knowlege would help a lot. You should also probably go buy a bunch of jets and try different things. Since your rich, you should tone it back a jet at a time untill you notice a lot better running and power. Your lucky Kehin carbs are easy to work on...

[Joel85350X]

Stock main jet on a 400EX is 148.

I think the idle jet is 42.

[ATC350X 85]

I can figure it out I just want to make sure i get the right stuff, i just dont want to take the carb off 15 times to get it right. :twisted: So should I just change the main jet or should I also change the idle jet? Right now it idles beautifully and I like that :-D

Justin

[Joel85350X]

Then all I would do is change the main jet from the 148 to something like a 140. The stock jet on a 350X is 138, so a 140 should be about right. You might have to go as low as a 138, but if you add exhaust or a higher flowing filter, the 140 will benefit you more. Leave the pilot jet alone if it idles good.

[ATC350X 85]

Yeah that sounds good, i gotta get it right i dont want to carbon up the motor. Im gonna try and get some jets tomorrow and do it up. Thanks guys.

[bad ex]

i,m pretty sure that the 400ex carb only works right on 300exs,and 400exs,you should just get a 350x crab.i think that would help you out,it's something to do with the diafram,i think the 350x carb does'nt have a diafram.kevin

[slothminx]

you got the delorean running! LOL this threads 2 years old. ive seen a ton of old threads dug up like this.

[bad ex]

Oops,i Didn't Even Look At How Old It Was.kevin

[Tri-ZNate]

hmm after 2 years I wonder if he rejetted of not :lol:

[kilabeez0]

this is just as bad as the kid who wanted a trike for his paper route 2 years ago! :lol:

[Tri-ZNate]

lol yeah that was good one.