It is difficult to be confident about what is happening without actually seeing and hearing the engine, Paul. You will recall that we investigated your Millers Falls chonda problem as if it were hunting, when it actually was ignition cutting in and out. They sound different, but until you've practised for quite a while, you would describe them both the same way. That is why I am not really confident that your problem with this Tecumseh is lean mixture. I do not think it could be a retarded camshaft: I'm regrettably familiar with the symptoms of that, from driving old cars with worn out timing chains, which occasionally "jump" their timing. It makes the engine very gutless rather than causing any other drivability problem (though of course it overheats the exhaust valves and destroys them if you try to drive it in that condition). An advanced camshaft, on the other hand, is mainly characterised by lousy idle quality and poor off-idle acceleration, rather like the behaviour of a racing camshaft. We need to be satisfied with your carburetor before pursuing camshaft timing as a possibility.
You have dealt with the main jet and emulsifier, which are the most likely causes of lean mixture in the upper and medium speed ranges. However while you are working on the carburetor, I think it might be as well to clean the main air bleed, just by squirting carburetor cleaner through it. Look through this instruction set on the Series 7 carburetor:
http://outdoorpowerinfo.com/repairs/tecumseh_series7_carb.aspGo to Item 14 for details of the air bleed. Do not remove the choke plate from its shaft, just see if you can blast the cleaner into the hole outlined in pink in that picture, and verify that clean carb cleaner comes out from the vent, outlined in blue. If crud comes out from the vent, it was worth doing. If perfectly clean carb cleaner comes out, it was a waste of time except that now you know it is clear. Then put the carburetor back together carefully and give it a test run.
