RE: This happens when a GY6 moped engine sucks a valve at 50mph
That looks a lot like the VW Bug engine I had that ate a valve many years ago. I still have the valve head somewhere - it was pretty firmly imbedded in the piston. I kept it to remind me exactly what the consiquences of misadjusted valves were.
And, yes, I had adjusted them myself the day before...
Apparently very poorly