http://www.blasterforum.com/engine-13/spark-plug-chop-20247/
Mid Range Tuning - The Needle
Now that we've done the top end and low end adjusting, what was the overall tuning direction of what you did?
Did you end up Leaning out the upper end and the bottom end? If so, chances are very good that it's Rich in the mid range too. (and vice versa if you were lean everywhere)
If you Leaned out on top and Richened on bottom (or richened on top and leaned out on bottom), chances are that you won't need to play with the Needle's settings.
This is where the Needle comes into jetting.
The Needle is inside the slide. You have to remove the cap that the throttle cable comes into. It just unscrews, pull it out and a large spring and a slide with the Needle will come out.
The Needle is removed by pulling the spring out of the slide body. You should be able to see it now. T here might be a retaining clip or washer on top of it. (once again, this depends on the carb - go use that manual!)
Now, this is a point that confuses people a lot.
To lean out a Needle, you need to move the Needle DOWN into the emulsion tube. You do this by moving the little c-clip Needle UP.
You richen the Needle by moving it UP - done by moving the clip DOWN.
You'll hear people talking lowering the Needle by raising the clip (leaning) or raising the Needle by lowering the clip (richen). You just have to stop and think about what was said.
Get the vehicle rolling, about 1/4 throttle and then feed in the throttle (you want to take about 1-2 seconds feeding in throttle - quickly, but not just snap it open)
What does it do?
Does it come off the bottom end well and then seem like it gets sluggish?
Then you're too rich - drop the Needle by raising the clip ONE position.
Does it seem like it wants to pull through, but just doesn't have any go? Then it's lean.
Raise the Needle by lowering the clip ONE position.
