Need Info on the Slide Needle.

jafo · Post by **jafo** » 05:11 pm Aug 20 2005

I need some technical info on the slide needle in the carb. I've been riding mine with the slide needle clip on the center groove, stock position. One question is if I go DOWN each groove or up ech groove, what does that change as far as fuel/air mixture goes? I want to try a few adjustments with the needle to see how the bike will react.

Jon.

Post by **KDXGarage** » 06:01 pm Aug 20 2005

If you take the clip off and move it down one groove, that makes it richer. Naturally, moving the clip up makes it leaner. Though all the jets overlap some, the needle affects mostly 1/4 - 3/4 throttle.

jafo · Post by **jafo** » 08:43 pm Aug 20 2005

Thanks Jason, thats just the info I need.

Jon.

Post by **Indawoods** » 09:49 pm Aug 20 2005

Indawoods wrote: If the bike bogs for a second before responding to throttle, lower the clip (raising the needle) a notch at a time until the engine picks up smoothly. If the bike sputters or sounds rough when giving it throttle, raise the clip (lowering the needle) until it runs cleanly. There isn't really any way to test the needle other than by feel, but it's usually quite obvious when it's right or wrong.

From:Jetting Guide
http://kdxrider.net/forums/viewtopic.php?t=1156

jafo · Post by **jafo** » 09:46 am Aug 21 2005

ok, so this needle adjustment would probably not help with anything I'm trying to do. From what you've wrote Indi, the needle controls throttle response. It's pretty crisp now. I don't want to loose any power, just the spooge out of the tail pipe. It's ruined two jerseys now including my new Kawasaki jersey.

I'm trying to eliminate the spooge. I dropped the jet size oncwe and it helped a ton. I'm going to drop it one more. I'll do the jet swap instead of the needle maybe. I'll read through the jetting guide first though.

Thanks guys, Jon.

Green Hornet · Post by **Green Hornet** » 10:59 am Aug 21 2005

The needle affects more than throttle response. Starting with the pilot, gas flow into the carb, then the needle-Gas flowing through piolt & needle, then the main, you follow. The needle position does have an effect throughout the entire range.

Post by **Indawoods** » 11:05 am Aug 21 2005

Jon,
That was just an excerpt from the article. If you read the entire article you will have a much better understanding of what does what.
Spooge is jetting though if everything else mechanically is up to snuff.

Indawoods wrote:"It's very important that you start with the pilot circuit. The reason is simple. The pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving."

I would drop the pilot one more and follow the Jetting Guide's procedure to tune.

Post by **KDXGarage** » 12:17 pm Aug 21 2005

You need to get your carburetor properly jetted.

I dropped the jet size oncwe and it helped a ton. I'm going to drop it one more. I'll do the jet swap instead of the needle maybe. I'll read through the jetting guide first though.

Which jet?? I would suggest that you buy several pilots and mains, then start testing, testing, testing.

jafo · Post by **jafo** » 01:12 pm Aug 21 2005

I have a set of main jets but need some pilot jets. I plan on reading the article too before touching anything else.

Thanks guys.

Jon.

Green Hornet · Post by **Green Hornet** » 01:45 pm Aug 21 2005

Inda-That is a great article, the easiest to understand out of the many I have read

Post by **Indawoods** » 03:45 pm Aug 21 2005

That was the intent!

jafo · Post by **jafo** » 08:49 pm Aug 21 2005

OK, I can't say a whole lot for sure yet until I can go out and test a plug at WOT, but I was running a 145 main jet, and a 42 pilot jet. I set the needle clip back to stock, then put a 142 size main jet in place of the 145 jet and left the 42 pilot jet in because thats the only pilot jet I have right now. I put a new plug in and rolled it out. I live on a corner lot and have sidewalks on both streets. I went out on the main street sidewalk becuase it's the longest one. It's about 40 yrds. long. I set the screw to 1 12/ turns out and started the bike. It idles well, kinda fast but sounds good. Good throttle response and took off burried the gas and shifted into second and had to shut it down because of the end of the sidewalk. I turned around and started back hit second and goosed it and the front end flew up. The bike never done that before. It was a pleasant supprise. The engine even sounds better, it's got that ring a ding ding sound to it now. I need to get it out where I can try it in 5th gear at WOT and then check the plug to see what it looks like. So thats where I'm at now.

Indi, I think it was you who mentioned that you replaced your stock needle with an after market one. Was that you? Where did you get it and what does it do for the bike? Do I need to do the R&B carb mod first before the needle?

Jon.

Post by **KDXGarage** » 09:13 pm Aug 21 2005

jafo: Good job on going down one on the main jet. Try taking the clip out of the middle groove and moving it to the "next to the highest" groove (from #3 to #2).

What engine related mods do you have onyour bike? No, I won't go and hunt down your bike profile

Isn't it a KDX220R? Do you have the stock carburetor (meaning 33mm not 35mm, nothing to do with an RB Designs modified carburetor).

Since this has turned into a "how do I jet my bike" thread, you may want to list your average riding temperature, humidity and elevation, in addition to any engine mods. My friend wsjkawasaki is down to a 38 pilot on his bike right now. Maybe he will see this and chime in with what other jets he is running right now. He is still in the middle of jetting his properly. I think he had a 142 main jet in his. I only got to do the "100 yard dash" on his bike, but from that little time on the bike, it seemed to work well. He had an FMF rev pipe and FMF silencer at the time. I don't know if he had his airbox lid off or not.

What did you mean earlier by dropping the jet size??

Just get a few pilot jets and have at it. I would suggest that you stick with the stock needle for now instead of making things more complicated with different tapers, thicknesses or lengths of needles.

Post by **Indawoods** » 09:36 pm Aug 21 2005

Jon,
I don't know very much about the 220 but the theories are the same when it comes to jetting. As Jason said, I wouldn't worry about the needle other than position at this point.
The pilot and needle adjustments should get you where you need to go. If you wanna step up.... RB is the way to go my friend!

canyncarvr · Post by **canyncarvr** » 11:47 am Aug 22 2005

Never..NEVER jet by spooge!

Yeah...in most cases you will find the drips are reduced with an approach to 'correct' jetting from a 'too-rich' situation, but one is not necessarily related to the other.

jafo · Post by **jafo** » 06:28 pm Aug 22 2005

Jason, what I meant by "dropping a Jet size" is that I had even a larger main jet in it before. I think a 148 or somthin like that. Went down or dropped to a 145 mian and now to a 142 main jet.

Now by taking the clip up one groove, thats going to lean it out even more, right? I just leaned the main jet out, so I'd want to do a plug chop before I mess with the needle, right?

Jon.

jafo · Post by **jafo** » 06:29 pm Aug 22 2005

I need to find some info on these carbs and read up on how they function. That would help me tremendously.

Jon.

Post by **KDXGarage** » 06:48 pm Aug 22 2005

OK, thanks for letting me know on the jets.

Installing the clip on a higher groove will indeed make it leaner, mostly in the 1/4 throttle to 3/4 throttle area. I'd be more worried about the main than the needle during a WOT plug chop.

Fool with the air screw some until you get a new, leaner pilot jet for it.

canyncarvr · Post by **canyncarvr** » 06:55 pm Aug 22 2005

Changing the needle isn't going to make a big difference...if any...in any plug chop test. Well, considering it's a WOT chop.

You can test the different circuits in the carb the same way as the WOT method. Fashion a stop of some sort to physically stop the throttle in the range you want to check, run it the same way.l

Seems a bit time consuming to me. If you're at all familiar with your bike, jet-by-butt does work.

re: How they function

Take a look at sudco's website. They have a throttle range chart there (and various other places) that shows different carb circuits and how they overlap.

Well...considering that a pooly chosen main jet (wrong size) effects the idle and everything effects everything else...it's a good reference tool to see what circuit works the most at what position.

cicone · Post by **cicone** » 07:06 am Aug 23 2005

This came up on the OTHER site a while back. I can't recall spooge ending up on the back off my shirt no matter how poorly the bike is jetted. The only time anything like that happened to me was back in the '70s.----oiled my chain with regular motor oil---that stuff flies everywhere---especially all over the back of your shirt. If that's the problem, then the fix is easy. Other that that, I'm stumped.

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Need Info on the Slide Needle.

Need Info on the Slide Needle.