When a 2 stroke mixture adjustment changes frequently, it's usually because of an air leak. Crank seals, mostly. And if it's a crank seal, make sure the crank bearings are good. When the crank "wobbles" on the bearings, the seals can leak.
I also wondered if some of it was sensitivity to ethanol gas. I know some of the older lawn equipment doesn't seem to like ethanol fuel like the newer stuff.
