LO206 yellow slide needle setting?

M

MikeleoneCT

Member
Has anyone played with the needle setting on a Yellow Slide gas 206? With it all the way at the bottom, it won't idle.

I just don't know if these things like to run rich or lean. We run a Jr Champ on asphalt, flat out.

Usually, lean is mean when you don't ever lift, but I don't know if that is true with these motors.
 
MikeleoneCT said:
Has anyone played with the needle setting on a Yellow Slide gas 206? With it all the way at the bottom, it won't idle.

I just don't know if these things like to run rich or lean. We run a Jr Champ on asphalt, flat out.

Usually, lean is mean when you don't ever lift, but I don't know if that is true with these motors.
Click to expand...
by lean do you mean ideal? Stoichiometric? I've never heard of an engine that will run better rich. When the mixture is right, the burning air fuel mixture will produce the most horsepower. If it gets too lean it starts detonating and that kills the horsepower.

To me, when someone says lean, I take it to mean below the ideal. So considering this, if you say, "lean is mean" it confuses me a little. I would put, "lean is mean" in the category of, "self evident truths". Of course many people use the term "lean" as the opposite of "rich". Maybe we could use the term, "very lean is mean", and, "too lean is bad".

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
If you have the clip on the bottom - you are full rich on setting. Now, while this is where I'd start out, along with the air speed needle backed out 1 3/4 turns, you'll have to have the idle screw cranked all the way in tight (do this without the slide in place so that you do not damage the slide.) Start with a float setting at .900."

With the clip on the bottom, you really can't get enough air past the slide (even with the idle screw all the way in) to make it idle -- however, if you set your throttle stop for idle so that the slide is slightly open, you can overcome the problem easily enough.

The right fuel curve should vary in fuel delivery at all rpms - it is not linear. I am not sure what you are trying to say, Al.

I will say this: I have heard of an engine that will run better rich. We run 4 of them every weekend. All 4 of them are small plate WKA flathead motors. Best power on them is found with very low egt on the dyno 8-900 max. Tune one for 1200* and watch it get lapped. That's not a theory, it the way every flathead engine builder has done it for years and continue to do so today. Not a theory; a fact and current practice. Just saying.



-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cuts
www.CarlsonMotorsports.com

Celebrating 25 years of service to the karting industry
765-339-4407
bcarlson@CarlsonMotorsports.com
 
I just bend the tab slightly on the kwik link to open the throttle more at idle - some adjust the cable up and tighten the set screw accordingly. Lots of ways to accomplish this.

Now, if you are running a long slide like the long black slide in the JR LO206, Jim's offset throttle linkage kit is the cat's meow.
 
12.2-12.6 a/f is where most of them produce the best power,this will also generate the lower exh temps Brian referred to.The best exh temp is the one that makes the most power.If your results don't agree with your theory,follow the results,invent a new theory if you must, but don't ignore the facts.
 
Exhaust temps can be deceiving for someone only relying on that. Just wanted to point that out in case somebody reads this and thinks all they need to worry about is the temp. Get the a/f right, do a plug chop and then take note of the exhaust temp for future reference. Thats how it seems to work best for me. With my two strokes. Am I right on this practice?
 
I ran it with the clip at the bottom. Even with the idle screw cranked all the way in and the mixture screw way out it still wouldn't idle. I was told that is how they are, and this is how to run them. Driver had to peddle it to keep it running, we didn't let it sit idling in the pits to avoid fouling the plug.

We won so something was working!
 
You are correct, Tom.

Mike, bend the arm on the throttle tab (Kwik Link) to hold the idle higher -- that way your driver doesn't have to do it. Problem solved. Yes, that's the way we do it too (because it works.) :)
 
thr2tom said:
Exhaust temps can be deceiving for someone only relying on that. Just wanted to point that out in case somebody reads this and thinks all they need to worry about is the temp. Get the a/f right, do a plug chop and then take note of the exhaust temp for future reference. Thats how it seems to work best for me. With my two strokes. Am I right on this practice?
Click to expand...
I've been teaching people the wonders, and the usefulness, of the EGT for years and what I told them is almost exactly the opposite of what you're saying. All of my hands-on experience has been with 2 strokes.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Al you do know if you go to far past lean that your egt actually drops? This is why an a/f with a plug chop will tell you if your egt is deceiving you or not. Been there done that the hard way. I am not saying egt is not important but don't rely solely on that. Sorry mike for crapping up your thread.
 
Mike, I have an LO206 from Brian. He is spot on. The thing doesn't idle worth a crap, but who cares as long as it runs like a spotted ape. FWIW (maybe nothing), I have one from Jimbo that idles a little better, but not great. It runs just as well. I have never compared settings on the two, cause lets face it, that's why I run LO206... so I don't have to.
 
thr2tom said:
Al you do know if you go to far past lean that your egt actually drops?
Click to expand...
I've been telling people that since the early 90s. That's 30 years ago. It's in my book. Do you know why it drops?
Fact is, I read a story about it, in Karter News, back in the 60s.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
stoichiometry I believe. Is when peak egt is seen and that's somewhere around high 14 low 15. The excess air cools the exhaust system which would make for a lower egt and more lean if you go past stoichiometry. Not good at explaining it. Am I even close?
 
You can run an engine out of fuel on the dyno at peak torque,full load w.o.t. and as long as it does not go into detonation,the exhaust temps will drop and the engine will simply shut off.Lean mixture detonation occurs when there is not enough fuel present to sustain continuous combustion and there are pockets or areas of unburned fuel left.Once the cylinder pressure/temperature rises beyond the threshold of the fuel tolerance,it will autoignite causing the severe damage we are all familiar with.Too much timing in and otherwise proper cylinder fill will cause the same thing to occur.Same result,burned and broken parts!
 
The cause of detonation is real simple; it's caused by excessive heat and/or pressure. There is a ton of things that can cause these conditions, chief among them, the wrong fuel, and/or the wrong air fuel ratio. With a 2 cycle, just changing the pipe can cause detonation. The point of the expansion chamber is, in part, to raise the pressure in the Cylinder. Some pipes do that better than others.


From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
CarlsonMotorsports said:
I will say this: I have heard of an engine that will run better rich. We run 4 of them every weekend. All 4 of them are small plate WKA flathead motors. Best power on them is found with very low on the dyno 8-900 max. Tune one for 1200* and watch it get lapped. That's not a theory, it the way every flathead engine builder has done it for years and continue to do so today. Not a theory; a fact and current practice. Just saying.
Click to expand...
read my sig again. Fact Always displaces theory.

I can't dispute your findings, I wouldn't try. My problem is I've never run a 4 cycle. I have raced 2 cycles. In every case, with a 2 cycle, the higher the EGT, the faster the kart goes.

It really puzzles me why plate motors have been found not to follow this rule.

Every engine builder in the world knows that the higher the compression, the higher the exhaust temperature, the faster the engine. It puzzles me why the plate motors don't follow that rule. It puzzles me that your engine runs best at 800 to 900 on the EGT. It puzzles me that, when you get the EGT up to 1200 degrees, it makes less horsepower. It is universally accepted that the hotter the burn the more power that is produced. It's all really confusing, for me anyway.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
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