OK, I got the 25LA running this morning, and clicked down the trim tab until I was flipping back and forth between 2400 and 2600 rpm. I set the needle to hold as steady as possible. After achieving the sound of a good tune, the engine would transition, again, 100% of the time. The only "problem" was that after more than a minute or so, the engine would start to sound like it was loading up. It was smooth as silk until then. A little jiggle of the left stick, and it always came back, but no jiggle=a "sputtering" flameout. I can't imagine that it's lean, as the pinch test resulted in a slow increase in rpm of about 500 consistently then a sag.

So, now I'm thinking that something else may also be missing. The airbleed hole is slightly larger in height (at about 1/16 inch), and double wide. I drilled it all the way into the carb, being cautious not to touch the needle seat. My carb barrel does seem to close the bore completely, and I can idle down to 2400 or 2600 or completely stop the engine with the trim tab. When the loading up starts (after a minute or so), I see rpm as low as 1900, before I jiggle and recover (or not). The airbleed screw threads are no longer visable in the airbleed hole.

Maybe it just needs some more run time, or maybe this old fuel is farther gone than I would have thought. With the fact that it does transition (2600rpm to 12,800rpm) and that it can be jiggled back from as low as 1900 rpm, I think I'm OK as far as the plug goes.

Unless this brings up some new (or different) thoughts, I think I'll just live with it, and be cautious of an idle below 3,000rpm. At 3,000 I doubt it will roll in our grass anyway. I'll just have to click down the throttle trim when I start to flare and settle in.

Bill, as for your Perry carb, I'm still not sure I can do the turning down. I might be better off trying to open the throat of the crankcase and just use some Permatex to guarantee a seal. Any chance that will work? Also, does the Perry mount the same (a screw from each side) as the LA carb, or will I need to create something?

Thanks again to Bill and Jan for the advice.