Just an update on my findings for future searchers...
I have finally moved away from tinkering with the carb. I have been adjusting and adjusting and adjusting trying to eliminate the lean-miss sounding sporadic put-put sound. From what I have found, these carbs are extremely forgiving. The 765 is still on my tractor and it is running.
My issues were not fuel related in the first place.
For giggles, I checked to see if the exhaust was actually blowing out the of tail pipe, or if it was sucking in whenever it would make the pffft sound.
It was actually sucking in, so the issue was not fuel related. I didn't want to get into a valve job just yet so I decided to try some snake oil remedies first, because this tractor does not get used unless I go on a romp or snow removal. I tried some water first. Brought the engine up to temp and set RPMs to ~1800. Removed the plug above the carb on the manifold and started adding a little bit of water at a time. I ran about 8oz of water through her and on my last little bit of water, I let it get sucked in and then shut down the engine. Replaced the plug in the manifold and let the tractor sit and steam for about 3mins. Cranked it back up, and no change...still sucking in through the tail pipe.
Went back to my shelf of tricks and got some ATF, did the same procedure. After cranking it back up, it wasn't sucking anymore but was very occasional. Did the same process again with ATF and now its sounding smooth. I knew the intake valves were horridly carbonized, but figured they were seating as I was getting fairly good compression readings, and the wet test proved that the piston rings were worn.
