I'm not sure how the carb on the KDX is. But you'll see a spring coming out of the top of the carb slide. Pull the spring out of the slide and compress it as tightly as possible. You'll probably see a small plastic ring at the end, leave it. While holding the spring, grab the throttle cable and if you look down you'll see a slit in the piece it goes into. Push the cable down and try to slide it out of the slit. Once you pull that out it's a breeze, get a socket that fits the head of the piece the cable came out of and take it out. Flip it upside down and the needle will fall out. I use needle nose pliers to get the clip off and on.
BTW, that plastic ring will have an "extension" (for lack of a better word) on one side of it. That fits into the slit so the throttle cable does not come out.
Hope this helps.