OK, got back on it today. I broke loose the line at the carb, splashed some gas down the bore and cranked it. I got good strong spurts from the fuel line, so fuel is getting to carb fine.

I shut it down, tightened the line, and restarted while shining a light into the carb. Only the front left bore is getting fuel. It's almost enough to maintain idle. Looks like the carb needs rebuilt. No surprise there. It would have been a small miracle if it didn't, after sitting for years.