KZ400 runs 60 seconds, dies...

I'm pretty much convinced the carbs are fine now -- and, yes, I removed all the jets and examined/cleaned them individually. Both times.
Anyway, once I'd started it with the petcock on reserve it ran each time until I attempted to get an idle without the choke. It idled with the choke, and ran fine without it with some throttle. I just never got it to idle without the choke.
Alas, it doesn't run at all currently, unrelated to the previous problem.
I decided to replace the contact points with newly-ordered ones, and then reset the timing. However, it was only after I'd removed the points and took the new ones out of the box that I realized they weren't the same set. Not even close, really. Either the dealer sent me other than what he'd advertised (and I didn't it fit on the plate securely), or someone has adapted non-original points to the bike. In any case, I reinstalled the used points, but it hasn't started since -- no sign of spark -- so I'm pretty sure I bollixed up the timing. Haven't had much time to fiddle with it since.