It wasn’t the carb. It was the piston. I had an overheat a while back, and the rings decided to stick themselves into the lands. I lifted the head, which was fine, and then pulled the cylinder. Once I got the cylinder off, I looked at the piston and thought, doggone it, it’s ringbound. I really did overheat the stupid thing.
The old Narda unit came back out and went to work for a while. Both rings sproinged loose, the lower after about 10 minutes, and the upper after about 30 minutes. The oil scraper was just nasty crunky. As the cylinder is clean and the piston is not damaged to the fingernail test, I’m simply going to wait for my gaskets and rings to arrive and will assemble it and check compression.
I am quite impressed that the oil scraper held 5bar. That is just awesome.