Hectic week [again] at work but I got some play time Wednesday evening.
Stood the tractor on its face. That seemed like a better idea than laying down looking up into a dark hole. With such long handlebars it was easy to tip.
Removed the plate on the bottom of the engine. Rod cap is the correct direction. Removed the cotter pins and rod cap. The engine has stood with water in it for [aparently] decades. The rod journal has a few deep pits from corrosion but it appears to have been turned in the rebuild and the babbitt is absolutely new. The babbitt hasn't been hot and no sign of it melting to the crankshaft. Nothing sticking up to grab, catch or drag. I went to the local engine rebuilding machine shop the next day and asked about the condition I found. These guys know about antique engines and frequently get to work on hit-N-miss and flywheel engines.
I respect their opinions.
They told me that pits in the journal surface will just hold more oil and with the engine not doing any work and only running a few hours per year that should be just fine for a long time.
I couldn't see anything about the main bearings through the little access hole. It was a trick to even get the rod cap out!
Put everything back together and gave it all new oil, overfilling it by quite a bit. I noticed that if the oil level is in the middle of the sight glass and the tractor is level, it seems to me that there is very little oil on top of that access plate that the rod cap dipper gets its oil from. Any sludge laying on that plate and it drives the sludge right into the rod bearing.
Started the engine and it ran great for about 2 minutes then it tightened up again.
I guess the next step is to pull the head. I'm thinking the cylinder is set up too tight. With any oil at all it really doesn't run long enough to build any heat in the lower end.
The last ATV I top-ended I made the cylinder too tight and it seized when it warmed up the first few times it ran. With a little run time it came out of it and was OK.
Kind of afraid to keep trying that with this one since Moog probably doesn't carry replacement parts.