main jet help!!!!

[franciscoluis]

Hi!
I jetted my 2000 400ex, and i put a 142 main and a k&n filter with outwear and the air box lid off, also i have the stock pipe without the spark arrestor (my alttitude is about 5200 feet, and the temperature is about 60º to 70º),
It runs slower than before and it has a lot of back fires.
Please help me out (what size of main jet do I have to put it on and the place of the clip on the needle)

I'll appreciate you a lot.
Thank you!

[YZROOSTINYA]

148 main is stock, are you running dynojet jets? they are larger for the same # jet.

[franciscoluis]

yes i'm running the dynojets, it a k&n power kit

It sounds like its now running too lean.

Make adjustments one at a time and record what you do and the results, that way you know whats going on.

Your elevation is gonna be part of the problem for many so try going up a couple sizes from stk (148) and dropping the needle clip to raise the needle.

See what happens with those changes and then make any needed adjustments from there.

[josh]

when does it backfire, when accell or decell or just on constant throttle, normally a backfire is a sign of too lean, i would go up a size on the main and put the little e-clip a notch or 2 down

[franciscoluis]

the backfire its when desell and also i have noticed that i feel thatthe power decrece a lot at full throttle.
Thanks

[mopar 400]

Your main jet is too lean, and you may need to drop your needle clip one notch. You may want to start at a 152 main jet and try to read the plug. If you pull your plug now it is probably white, showing your lean. If you richen it your plug color should change. This will cure your backfires and lack of power.

[josh]

what kind of fuel do you use with it also, pump gas runs richer than av gas, or anything that is 100+octane, but the backfireing while decell means you are a little lean and the e-clip needs to go down a notch

[franciscoluis]

thank you all.
as a matter of fact, today i'm gona take my cuad to the mechanic. its a friend of mine. so tomorrow i'll tell you all how it end.
thank a lot
Francisco

[PimpinPapaZ]

The stock jet (148) should be just about right with the airbox lid off at that elevation. We run stock jet, lid off, Supertrapp/12 disc @7000 ft elevation.

[Gusto]

If your running your dynojets-bump it to a 165 for your alt and If you changed your needle put it at the second setting...that should put you in a real close ball park...when it starts to get warmer out you'll have to change the main once again. I run at your alt and have found these settings to work just fine.