OK. I rode the new setup up and down the street when I finally got it put together.
Set it in the garage for a night, wouldn't start up the next day. Sounded like "whuf whuf whuf [twist throttle] pokka pokka pokka pokka [return throttle] whuf whuf whuf ... whuf ... whuf ... whuf DIE.
OK. Sounds like flooding. Disassemble carburetor. Eventually find a tiny grain of playground-like sand jamming the jet. Blew out the carb with carb cleaner (by the way, don't look over the carb when spraying carb cleaner in there. I'm expecting a tumor on my eyeballs soon.) Slight adjustment to float switch to close off flow sooner.
More oil in throttle line. Now slides pretty well. Also bled the fuel line and changed from 32:1 to 20:1 for break in. Cleaned out the in-tank filter. New plug NGK B7HS. Moved petcock to restrict fuel flow just a little.
Start down the road, whuf whuf whuf pow pow pow! Yay!... Screeech! Ooooh. Chain jams. Dang. Clean dirt off chain and out of clutch case. Lube chain. Whew. Nothing torqued out of whack. Take the bike back out.
Still bogging. Dang. Almost had it. OK. Maybe air leak/losing compression. Applied gasket goo to manifold intake from carb if leaking there. Still bogging.
And here I am. So close. Tomorrow I'll see if I can check the head gasket for leaks, and maybe seal up the carb bowl better as well.
Any other ideas?