I may not be all caught up on this thread, but I seem to remember you saying that the timing marks looked slightly off relative to the surface of the head. Seems like your hunch about being off a tooth is warranted. What a bummer.
Honestly, I was really considering doing a 300 swap on my pre-gen, but I like my adjustable valves
That, and I've come to the conclusion that I can easily override the suspension with this old 250 mill! More power on this little bike would put it in a ditch