It sounded very eager to run today. I got a handle on the incipient binding on the big end - yes it is tight and needs some clearance, but the bug end bushing is actually a bit thicker than the crankpin, and although it turned freely when assembled there was next to zero clearance, there were swirls/fret marks on the backplate. Maybe some fine swarf got in there too. Anyhow it tightened up just as it faded out, and did not seize. So it came apart and cleaned up fine. Piston and liner are peachy. This would mark the first time I have installed a non-original connecting rod in an engine before, so it didn't occur to me to check that dimension. This is definitely my speed trainer engine.