Ok, since I had reason to believe I had spark, air, fuel, and compression, I started looking for timing or other stuff that could be wrong. I eventually found
isaac's thread called "No start: Have spark, have fuel, have air" in which he discovered that his woodruff key had been shorn off, thus allowing the flywheel to misalign and screw up the ignition timing.
If you'll remember from last page (about a month ago), I intially didn't tighten my flywheel on tight enough, well, as it turns out, that destroyed my woodruff key.
It took some time to figure out how to get it out, since the protruding part was completely flattened/gone.
Turns out that the semi-circular shape means you just have to push down on one end (by, say, tapping an awl on it with a hammer) and the other pops up and can just be pulled out, so it's not really an excuse for your friend to build his arc welder, but whatever, we got it.
I put a new one in today with great hopes that it would go, but it didn't. It was hot and it took us a long time to tighten everything down on my bike all proper-like, but yeah, it won't go. Turn over sounds, no catching. I'll take another look at it sometime next week, I guess.