250-500cc Where do I go from here? Engine issue..

It does have a power valve but the damage was done on the intake side of the piston..

Looks like you skipped step #1, wash the crud off the bike that could fall into the engine. Time to pull the motor & split the cases. Good luck with whatever course of action you take. They are nice bikes. Hope it all works out for you.

I think oldbikedude has nailed it. There's a lot of metal in those pictures, you need to figure out where it came from and what damage it has caused. I think a complete tear down and inspection of the entire top and bottom end is in order. You can do it yourself, just be patient and careful, shoot a lot of pictures and take notes. And yeah, clean all the crud off of it first.