Okay, Geist .. looks like a discussion about Carburetor dynamics is called for.

Two circuits in a carburetor. . Main, and Idle. Both do different things at different throttle settings.

We'll start with the Main. Basically it controls fuel down to the point where airflow through the carburetor is too low to effectively drag gas out of the Main fuel feed Venturi. This is usually below 1/8 total throttle blade opening. If they made the Main capable of flowing gas at lower throttle settings than that, the top end would be restricted, or the fuel curve would go overly rich when you started to get a lot of airflow through the carburetor. So, to enable the engine to idle at lower rpms than about 2000-2500 or so, they add an idle bleed right next to where the throttle blade closes in the carb throat.

Basically what happens with Idle fuel feed is that at a nearly close throttle plate position the air is forced against the small hole for the idle mixture gas, and causes a low pressure area, which pulls fuel into the airstream, allowing the engine to continue running. The farther you open the throttle blade, the less the vacuum on this hole, and the less idle mixture gas you get into the engine. Idle mixture is effective up to about 1/4 throttle at most, at which point the throttle blade opens too far for air to be forced against the outlet, effectively cutting off that source of gas and making the engine depend only on the Main mixture coming from the top portion of the carburetor.

What it sounds like you are doing is getting the throttle blade into a position where the Main fuel feed is crutching the idle mixture as well, basically an off-idle position, not a true idle. It may work, but there are problems involved with it. What you SHOULD be doing is closing the throttle blade as far as possible, and adjusting the low end mixture needle to achieve the lowest possible idle setting, then backing it off a hair (usually about 1/16 turn from that point) and then setting your idle speed to about 1100-1300 rpm. You ridle should sound smooth, but not TOO smooth. An occasional burble or misfire is perfectly fine at idle. We are not trying to have an idling contest here. . we are trying to keep the engine running when we close the throttle while flying, and a slightly richer mixture helps with this because the engine tends to cool down while the plane is gliding, and too lean of a mixture can lead to stumble or even a flameout.

You want to set your Main mixture by checking it at half throttle. You want half throttle to be SMOOTH. . .no burbles, then as you slowly close the throttle to about 2-3 clicks off idle (where the idle mixture will start to come into play) the engine should start to slightly burble or misfire. If it does not, then you are too lean on the top end. Set your top end needle to where the engine just starts to run rough when almost at idle, but not really rough. . its more a slight stumble/burble every second or so at about 2000-2200 rpm than a constant 4-cycling effect. Once you have those two parameters set .. a decent idle, not TOO smooth, and a clean midrange with just a hint of burble toward the bottom of the throttle settings, try a few medium speed transitions from idle-full throttle.You do NOT want to just slam the throttle full open. . first off, the servo is going to take about .2-.25 seconds to make the transition, a lot slower than your thumb moves, and secondly its a BAD idea to ever do that anyway. You want to operate the throttle smoothly at all times. Slamming it open can cause flameouts or rough hesitation as the carburetor tries to get enough gas into the airstream and the engien has to wait for it to arrive so it can run properly. After you've checked it all over. . made sure it transitions smoothly with no hesitation and runs well both at full power and idle, let it cool down and see how it starts. Some engines are a bit cold natured, and will require a couple of restarts to run properly (all my 3W's do this. . just the nature of the engines) If the engine starts well and holds idle even when cold, it's probably just a little on the rich side, and you can play with the needle slightly to lean it out a little more. When you start having problems getting the engine started, due to the mixture making the engine cold natured, open the bottom end 1/16 turn at a time till the problem is resolved, then leave it alone unless you have furhter problems. Always try to set the high end for best transition. . NOT best Power. I have not used a tachmoeter to set a needle in about 3 years now. I do check top rpm from time to time, as well as idle rpm, but as long as I can kill the engine using the throttle trim, and I have a clean, slightly rich, midrange transition, and it starts the way it always has, I don't even bother with a Tach. You can lean an engine to achieve an extra 50-100 rpm on the ground, but it's running characteristics in the air may tend to become questionable, which is why I advocate a slightly rich mixture and setting the engine up for midrange, decent idle, and good transition, instead of overall power numbers. Aftter all, the thinking goes .. if you REALLY need that extra 100 rpm or so, you gotta ask WHY. . if its necessary, then you need a bigger engine. If you are just trying to impress people, well. . that's a different story. I don't concern myself with top-end rpm numbers anymore. . they are not what's important. . what IS important ishow well and dependably the engine runs at all times. N ot tweaking for the last 50-100 rpm will result in a better overall running engine throughout the rest of the flight.

After you get it set up, its must a matter of keeping an eye on it. Mosty gassers seldom require readjustment of the needles.

Hope this helps.