Yeah, I made a few changes to the wording, to clarify.
I'll go up and re-read your posts to see if anything strikes a chord, might think of something else.
Okay, so I think you said you've got a lean off-idle.
One thing it could be is aged metering diaphragms. These should be almost as soft as rose petals, not dry and stiff like cardboard. If these are stiff, the idle and off dile fuel mixture will always be too rich or too lean depending on which way that stiff diaphragm is being oil-canned.
The other, probably more common possibility could be an accelerator(acc) pump issue. This little pump attached to the PTO carb(rear carb) shoots a shot of fuel down into the carbs when you crack the throttle open, there's a cam on the throttle shaft that pushes the lever which in turn pushes the acc pump diaphragm plunger. The reason is, it takes an instant for air velocity to increase through the carb bore enough to begin pulling fuel from the chamber through the pilot jet and through the three transition ports just above the throttle plate. Mid-range circuit, I'll call these three transition ports, b/c it's a long transition from when they begin to flow and the main circuit gets going. During this time when the throttle is first cracked open, you might notice a lean stumble if the accelerator pump didn't shoot this small volume of fuel the instant you begin moving the throttle open.
So you might be wondering how to determine if the acc pump shot is adequate? First, look down into the carb throats with a flashlight and watch as you actuate the throttles from off idle. You should see a healthy shot in both carbs, like out of a windex bottle pump or something. Not just a little dribble.
Second, if that looks good and the lever gap is there but very small, you may as well look elsewhere.
So if you crack the throttle open a hair and it immediately feels strong (as if the acc shot of fuel was there and by the time it got used up the mixture went lean again) then I'd have to think of confirming pop-off or as a test, opening up the mixture screws a bit. Those screws are really only there to adjust throttle-closed idle mixture, so pop-off would be my first focus b/c the vacuum should have built enough on the first burst of power to have begun drawing fuel through the transition ports and also pull the metering diaphragm into the chamber to open the metering valve. If that spring is too strong, the delay could be too long. Lowering pop-off would especially be in my focus if the factory air box was long gone. If pop-off is too low, you'll have too much fuel coming through the low speed circuit, maybe even enough to dribble out of the high speed venturi, while idling. Even a new metering valve can leak with engine vibration if the pop-off is set too low, possibly resulting in flooding out from excess fuel.
Accelerator pump:
The acc pump nozzles may be gummed, or even the acc pump timing(assuming it's a lean condition) may be too late. I didn't have any lean issues coming off idle, but the acc pump cam lever gap to acc pump diaphragm plunger wasn't .0050 like it's supposed to be, there was no gap at all. So, I adjusted it to make sure the acc diaphragm plunger could return to it's stop, just a hair of play there after adjusting idle speed. I'm sure that's why they spec a gap there so the pump can draw in a full charge, considering the shape of the cam and all. I just put about 0.0020 there to give me a little room to adjust idle and still let the diaphragm spring fully reload the acc. pump. I can wiggle the lever freely back and forth just a hair, as it is now, just took the tension off of it.
The accelerator pump wasn't my problem, despite the fact it wasn't properly adjusted for my throttle plate position. Maybe the original idle was 1200RPM, I don't kow, all I know is it was too low for my tastes, I set it to 1400 and checked it didn't idle much more that 3000 RPM out of water, it idles about 3050-3100 out of water. If it ever runs away, I'll probably be wondering if a crankshaft seal is leaking air.
Anyway, my lean bog was nearly just out of idle too, but it didn't lean die easily, down there. This bog extended just past 60% into the throttle, with RPM over 3000, if you jammed the throttle it wouldn't tend to bog but if I moved the throttle slowly, it wasn't until past 4000 before I got out of that lean region. At the dock, if I played with the throttle enough, it would occasionally lean die, mostly around 3000, like with the bucket down and hitting it to slow the boat.
I cleaned, checked, rechecked, everything multiple times. Finally went up two sizes on the pilots to 80, and now she pulls like a mule with no hesitation anywhere in the throttle range. The second thing I did while in there b/c I like my 2-strokes fat anyway, was put an 80 gram spring on the diaphragm needle(Okay, I made a little white lie in my earlier post re:95gr spring, for which I don't really feel guilty). I like to make big changes.
So, the way it's tuned now, I can hear just a hair of four-stroking a bit off idle, like maybe around 2500 RPM. I'm guessing the diaphragm metering valve opens just a bit too early(80gr spring). It's not a performance issue, just I can hear the extra fuel four-stroke and clear out, can barely even feel it less than a second, if that, when I move the throttle slowly open to accelerate from idle to "no wake" speed.
So next time I'm in there, I might install the original 95gr silver spring and call it done.
2-strokes: Go rich, and come back till it no longer is too rich. I like a bit of smoke along with an occasional touch of four-stroking, that way I know she's not lean and she's getting the fuel necessary to carry the oil.
