"It ran well when I parked it!"

[Patrick L.]

I'm kinda surprised that it won't free up. With soaking the heck out of it from the top [ thru the plug hole] and at the guide, then prying straight down or as Tom suggests tapping down on vise grips.

It seems unlikely but I wonder if somehow something got stuck between the face and seat and bent the valve.

Again, if it does free-up, roll the engine over a few times to make sure it stays free before putting it back together. It may take a few more squirts to keep it free.