The problem with ring pieces in the engine is you pretty much can't guarantee you got them all out leaving the engine in place. I learned the hard way on an old DT1. I'd pull the engine, wash out the crank area of that bore, flip it upside down, spray air in there to make sure it's clean, make sure the crank spins freely, then load it back in and try again.
You'll probably find most of it in the exhaust pipe. Check the exhaust port at the top. That's usually where they like to grab the piston. Check the piston and make sure the arrow is pointing to the exhaust.