Well. Disassembled the left-side carb and cleaned the hell out of it. Replaced various O-rings, but not did not remove the butterfly or replace its O-ring.
Put carb back on the bike and immediately noticed a difference. Still hard to start, but ran on both cylinders. Played around with the choke, got it started and running. The noticed overflowing carb bowl. Bad, especially given the hot exhaust pipe immediately under the flowing gas! Turned off the fuel, cleaned up. Will need to check float. Suspect it is more of a “sink”, at this point.