Some progress was made today.

After idling it in it's current state, removing the seat and various other things that were in the way, I was able to spray carb cleaner into the inlet while it was running, which would cause a really smooth jump to about 2000 RPM momentarily, sounding as a bike should sound.

After doing this on and off throughout the day, I went through all of one can and just started the second can, all four exhaust pipes now get hot, whereas originally only two did. So now I know *something* is getting through all four carbs. That's a good sign I think.

I guess I shall figure out how to take the tank off, then the intake manifold, then all the "I'm sure they're dryrotted and frozen" 2" (or so) rubber tubings between the intake and the four carbs, and the four carbs and the cylinder heads.

Thanks for the advice and such. I'll take it apart and soak it like you suggested.

Part of the "scary" factor is I have little to no carb experience, and this thing has four of 'em. A holley 4bbl I can get right, sometimes, something this complicated seems to worry me. It's also not my bike lol.