I Need Jetting Help!!!

[trailrider894]

I need some serious expert help with my jetting!! i have never jumped into a carb before in my life on a quad. I have a 2000 400ex with a White-bros e-series pipe, fmf powerbomb header, K&N w/outerwears and no lid. i have played around with the carb settings before and my plugs are always always black when i pull them out of the quad!!! even after one ride. and the quad has no power and i would like to blame it on jetting. i would like some suggestions on what i need to run as far as the jetting??

Is the jetting factory? Or has it been played with before?

[trailrider894]

it has been changed by the owner before me.

[trailrider894]

it's backfires a-lot on warm-up for the first couple minutes and pops when de-accelerating. PLEASE GUYS I REALLY NEED HELP!!!!! if you can't help me please help me find someone that can!!!

[trailrider894]

bump!!!

[alberto]

trailrider894,

I am no expert but, having black build up on your plug is a good indicator of running to rich. That's OK cause from what Ive been told its better to run rich then lean.

So I would start by going down a jet on your piolt and main. That should be a good starting point. Then you can adjust from there. As far as the back firing that is an exhaust leak. Thighten all the nuts and bolts on your exhaust starting at the header and work your way back.

I hope this helps. Tuning your fuel/air mixture is one of the more involved projects. Take your time and be patient. Remember messing with these things is half the fun. GOOD LUCK.

[trailrider894]

okay well it mostly was back-firing after i added more disks to my exhaust. it does have small leaks at some spots. what can be used to fix these leaks??

[trailrider894]

what i'm really looking for is what size Pilot jet and what size Main should i use and were should i set the clip on the needle??

[trailrider894]

also where should i set the fuel mixture screw??? i'm at right around 900ft and the weather is now in between 70-90 degrees.

[alberto]

Disks? Explain.

If you want to make sure that you are running the right jets there are many things to take into consideration. First and foremost what is the elevation that you are riding. Second and probably the more difficult where in the powerband are you running rich. Do you idle rough? Are you losing power in the higher gears? Or are you rich all the way though? According to your signature you have a DINO JET KIT, this kit has several different jets you can change out. I have my clip set 3 from the top with 2.5 turns on the air mixture.

Like I said half the fun is messing with your bike, just take your time.

[trailrider894]

900ft is the elevation. it idles just fine and i don't let it idle very much. yes i lose a ton of power in the higher gears!!! i feel like my EX is a 2 ton hunk of crap sometimes it just doesn't wanna go!!

[alberto]

ok now were getting somewhere. Let it idle until reg operating temp and give it some gas. If it bogs and dies then pilot jet is lean. If it revs nicely with no black smoke then your pilot is good. So we can leave that alone. So I would change your main jet one size down and go for a ride. You should see changes in your top end. It would also be a good idea to replace your plug after each jet adjustment. It will tell you if the changes are working. Hope this helps.

[trailrider894]

okay i let it idle and it just bogs when you hit the gas the first few times and shoots out a little bit of black smoke.

[trailrider894]

BUMP!!!! i need this thing fixed soon!!! ( the disks are for the White Bro's exhaust. Just adds more power and makes it louder.

[alberto]

Have you checked the thread on the 400ex forum? Its a sticky called "jetting help"

I just dont want to give you bad info. Considering that tuning your quad is one of the most difficult things you will ever do.

Have you tried changing any of your jets? Cus I still think your running rich. I would go down on both your pilot and main too.