Minor update - the scooter's back together again, but it's not running as well as it should be - or as well as it was for that matter. So, time to start troubleshooting it and figure out what I screwed up and if it's fixable or not. Otherwise, I'll probably just replace the head, cylinder, and piston. That'll be about $200. Not ideal, but gotta do what ya gotta do. We'll see.