Clay Pigeon
Shooter
With an aluminum head engine, almost anything is possible on cool down. Could have finally lost that head bolt that was just hanging on, the gasket, dropped a valve seat, etc. Could have run it out of gas and leaned it out that one time too many last time too. We simply don't know.
I wouldn't drag Jay over the coals here for that suggestion. The entire point of trouble shooting is that it's a process and that's one of the only things OP hasn't been able to check. He already did everything that made sense, so it's time to start looking at things that don't make sense, IMHO.
Its as simple as this, its prudent to correctly diagnose a no start correctly with a test light and or a meter and find the bad part or connection. And then go and buy the bad part.
Otherwise one is running blind replacing parts. INGO is full of folks that blindly tell others what is bad without any knowledge of whats really going on.
All theses members that know so much about electricity, but yet can't use a meter or tell someone else to use one.... I'm out...
Good Luck OP....