Sun came out today, so I messed with it again. Long story short, I think I have it "fixed":
This carb has a float, needle and seat. The seat is replaceable, and it uses an o-ring. These o-rings can dry out (it's mentioned in the service manual) and mine was dried out. I suspect that was the initial problem: the o-ring shrunk in cold weather enough that it just kept flooding out.
Then when I rebuilt the carb I put the main jet needle in wrong--there was a piece I put in wrong, and it was not being pushed down properly I think--I found this mistake today, fixed it to no change (see next problem) so I'm not positive this was a problem. But it surely did not help.
Last weekend I tried to adjust the float up and down, as I noticed that gas kept coming out of the carb, one of the orifices (not sure which one, might have been for air). Figured the level was wrong, but just would not respond properly, and then it got cold outside.
Of course the cheapo fuel line I bought failed, and a couple weekends ago I tried to use an electric pump as a quick hack to bypass everything, as nothing made sense (too much fuel? too little? initially I was not sure). Today it dawned on me: despite being a small pump, perhaps the needle was being overwhelmed. Rigged up the original system and... it idles and moves and runs more or less like it should.
Of course, I lost a screw to the float bowl, the throttle cable won't seat properly, I couldn't route the choke cable properly and I have to figure out how to replace the fuel line, then I can fix the ignition wiring that I cut apart... One failure fixed, three more knucklehead fixes left to go.
[I put part 4 under part 5, so I think jet needle 6 was hanging up.]
