Slide needle question

[Tenrilid]

Hey gurus, I have a seemingly basic question. What is the purpose of the slide needle and what effect would changing the position of the slide among the 5 slots inside the slide?

[Big T]

The needle controls the amount of fuel coming out of the jet. Its thickness and taper varies in different models to allow the correct amount of fuel mixture to occur at a given throttle opening.

Raising the needle up (lower in the clip position) allows more fuel to come out earlier. Lowering the needle does the opposite

[Dave8338]

And that's all's there is to know's, people...

Some of the aftermarket kits, will have needles with a "thicker" taper than the stock needles. Depending on what mods you have done to the bike, this may work for or against you, when fine tuning your CV's...

[Tenrilid]

cool. that's pretty much what I figured I just wanted to get a confirmation that my assumption was correct lol! So, with that in mind, moving the needle up would only effect the fuel flow at almost any rate below wide open throttle?

[1980GS1000E]

From closed to open throttle it goes like this, simplified:
pilot jets>needles>main jets.
Fuel ratio from approximately 1/4 throttle to 3/4 throttle is heavily dependent on the needles.

[koolaid_kid]

From closed to open throttle it goes like this, simplified:
pilot jets>needles>main jets.
Fuel ratio from approximately 1/4 throttle to 3/4 throttle is heavily dependent on the needles.

Absolutely. Carrying this one step further, if you lower the needle by going up a notch, you are in fact raising the point at which the main jet starts to take effect. And vice-versa.
One thing you might want to take a look at is the washer mod. Basically you replace the plastic washer with 4-5 1mm stainless steel washers. It eliminated a slight flat spot right off idle for my stock bike with stock carbs. Or course, I did not have the luxury of multi-slotted needles, I only have one.
Edit:
Here is a thread discussing it. I got true metric ss washers at Ace Hardware. It takes the 1mm size.

[86turbodsl]

Unless you really know what you're doing be careful. There's a whole bunch of different needle calibrations. I've been slogging through this for a while now trying to get my GS jetted right.

[Tenrilid]

Unless you really know what you're doing be careful. There's a whole bunch of different needle calibrations. I've been slogging through this for a while now trying to get my GS jetted right.

It was more of a curiosity situation. I am the type of person tha likes to know HOW stuff works, not just if it works when I put it together/plug it in lol.