Just saw this thread was revived. My issue is resolved. An animal chewed thru the fuel line coming out of the fuel pump on the back of the engine. Unknown to me, it was dripping gas all the time. I was mowing, and came back to the shed overhang where it lives, backing up, when I felt heat on my back- there was a fuel fire on the back side of the engine! Fortunately, it was 10' to where I keep a fire extinguisher in the barn, so it was soon put out. I guess it had been dripping, but as long as the mower was moving forward, no fire. When I backed up, the gas dripped onto the hot muffler, and... I pulled both tanks, cleaned them, replaced the fuel lines, cleaned off the plastic air cleaner housing that had taken the heat, and no more stalling issues. Might have been debris in the tank? My problem now is oil leaking into the cylinder(s) when it sits for more than a week or two, causing smoke upon start up. Clears up in a moment or so, and not using oil, so I am leaving it alone for now. (well, now it's winter, so I am really leaving it alone.)