carb internal question

[killer400ex]

i just re-built my motor and am in the process of tuning the carb, i have a 00 400ex carb, i called up dynojet and they told me for the mods i am running and at 400 feet above sea level that i should be running a 170-175 main and a stock pilot, but my problem/question is that i cant adjust the needle, it is fixed to the slide itself not allowing for the diffrent settings, but the main jet itself is on this stupid weird screw that will either bring the jet further into the carb or bring the needle further into the jet, or bring it out of the carb or bring the needle further out of the jet but i hear people all the time talk about the needle being on different clips, i was just wondering if the only way to adjust it is through the actual screwing in or out of the main jet, but here comes the problem, in order to adjust this i have to strip the carb out of the motor, and i have to take the fule bowl off the bottom to get to it since i cant adjust it through the main jet hole on the bottom of the bowl, this is how i have been dooing it but it takes an hour to try 3 diffrent settings! any advice would help alot since i need to get this thing out of my vocational school soon

[the Z Man]

Your main jet is accessed through the 17 mm nut on the bottom of the carb.
The needle can be adjustedby taking out the slide, removing the screw and adjusting the clip up or down.

[killer400ex]

thats how both me and my mechanic though it worked but we looked on the slide and couldnt find anything, also why would the tube the needle sits in be adjustable? shouldnt this be fixed and not the needle? wow this is a pain in my balls

[the Z Man]

Go to rivamotorsports.com , they have an online parts finder, the picture clearly show the needle is adjustable.

[killer400ex]

oh ok, i just looked through the clymers book and read up on it, but i still dont know why both are adjustable, it just makes it harder to get it how you want it

[F-16Guy]

Okay, my advice:

1) Don't use DJ's stage 2 jetting, it's WAY too rich. Use the stage 1 guide and go up a couple sizes on the main (probably about a 155-160 if I remember correctly).

2) Install a 42 pilot jet regardless of what DJ recommends, and turn the fuel screw out about 2.5 turns from closed.

3) The main jet isn't adjustable. It meters fuel based on what size the hole is, and cannot be adjusted aside from drilling the hole to a larger size. To "adjust" it, you need to change the jet out with the next larger or smaller size. With the DJ kit, you just want to change the small, round-head piece with the number on it.

4) The part you are attempting to adjust is the jet holder. If it's loose, you'll need to remove the carb, remove the float bowl, adjust the jet holder so that it's back to the stock height (or as close as you can get), and then tighten the lock nut so that it can't move anymore. Once that's done, install DJ's main jet adapter tight enough so that it won't loosen when you change jets next time. While the carb is apart, install the 42 pilot jet using the guide in the "Articles" section at the top of this page.

5) Take the slide out of the carb by removing the two small phillips screws down inside the slide. Next, pull the spring up to give the cable some slack and unhook the throttle cable from the slide. Use a phillips screwdriver to push and twist the needle retainer to remove the needle. Install the DJ needle with the clip in the middle slot and the washer on top of the clip. Re-install the needle and slide and install the carb.

[richards]

Originally posted by killer400ex
my problem/question is that i cant adjust the needle, it is fixed to the slide itself not allowing for the diffrent settings

Some of the 400ex's came with needles that are not adjustable. That's what my 06 had stock. There are no notches on the needle so you cannot adjust it the normal way.

But check to be sure that is what you have first... You have to remove the lever mechanism from the top of the slide, then pull the needle out. It will either have a fixed clip like my stocker or it will have a removable clip with several notches.

If yours does not have notches and you want to richen it up a bit at mid throttle openings then you can use a shim or washer to shim that kind of needle up a mm or two. If you want to lean the mid throttle openings you will have to buy a new needle that has notches so you can adjust it down a bit.

[killer400ex]

i knew that i was screwing with the jet holder, and i dont have a dj kit i just have the jets left over from the previous owner, but adjusting the jet holder did the same basic thing, it is just harder, but i am going to go to my shop tomorow morning and try this out, i have a computer in the class so i will let you know how it works out, it has been sounding a tadd bit rich but i will have to wait till i get the swing arm to see how it runs through the rpm range, but this information will definitely help me out alot

[F-16Guy]

If you have Kehin jets, you should be running about a 162-165 main and a 42 pilot, and the stock needle with the clip in the stock location or one slot down (richer), depending on your preference. Messing with the jet holder isn't going to change the mixture. The needle jet is what the needle uses to meter fuel, not the jet holder, so moving the jet holder just moves the main jet up and down. You should find the correct main jet first by trying different jets around the range I suggested and seeing which one gives the strongest wide-open-throttle performance. Always do the main jet first, since your needle settings could change with a different main. Once you have the main with the best WOT, you'll need to ride it through the throttle range and see if there are any lean or rich spots in the middle. If there are, raise or lower the needle to fix any mid-throttle problems. Finally, adjust the fuel screw for the best idle and snap off the bottom. The settings I suggested should be really close for a 11:1 426cc. I have a 11:1 416cc with a stage 1 HotCams cam, and I'm running a 162 main, 42 pilot with the fuel screw at 2.5 turns, and the stock needle setting, and it is spot-on.