What would cause the skirts to break on a piston? What would cause the rings to break on another piston? The engine is a 97 zrt 600.

Excessive piston to cylinder wall clearance- on both counts. Things don't last long in these when they get loose. Both pictures of the same engine? How many miles? You still need a jug?

rings can break out also if they catch an intake/exhaust port or if you dont have enough squish band the compression will cause the edge of the piston on top to break off letting the top ring move where it shouldn't go. the skirt you show looks like piston slop to me. were you able to find the missing chunks of the skirt? If you ran out of oil that could cause the skirt to score bad and maybe break before it seized up, or if the motor was ran to hard when it was cold it could do the same thing.

Yes, both pics are from the same engine. I still need a jug. I am still trying to get the clutch off so I can take a better look at the crank for some extra parts. Once I get everything figured out I will be giving you a call irondog. Do you have more than 1 cylinder for sale?
Sled has 5,000 miles. My brother bought it used 2 years ago and ever since day one we had issues with it. Once it would start it would have tons of power. It used more gas than my truck, which is hard to believe. Then this year it started making noises and then stopped working all together. Once I took it apart I realized there was no carb tuning that would make it run any better, lol.
It doesn't get too cold out here and we would usually let it warm up before going out but who knows what the people did to it before.

Yes, I have several cylinders and many other 600 ZRT parts.

Awesome! I think I'm going to be needing a lot of parts on this project!

Cylinders can be re-plated to look like new for less money then a new or maybe even used cylinder.