Well yes and no. The piston obviously blew and blasted the cylinder walls. If it’s not to bad you can bore it out and go a little bigger on the piston. Going to need a new jet kit for the carburetor as well. Now, if the cylinder is shot then you can possibly pick up a used cylinder maybe from eBay and go that route. Or buy an aftermarket cylinder set up. The metal parts that came off the piston went into the crank case. They can be flushed out. Also you have to check the main crank and bearing for play. Have you noticed anything else that’s possibly damaged as well?

When you changed the stator coil the new pick up was not with it? They are usually bundled and wired together. An intermittent spark usually is a loose connection, worn ignition contacts or an over heating part. Check the secondary ignition coil and the spark plug wire coming from it. I’ve seen pick up coils fail after they get hot and work after they cool down. I would go over all the connections, grounds etc and start there. Then get into the more invasive stuff. Wiggle the ignition key while it’s running. If the bike shuts down after a while be ready to test the pick up coil with an electrical tester to see if it’s getting hot and breaking down. Check the regulator/rectifier that’s it’s not getting hot or failing. Look up the spec in the electrical portion of the manual and it will tell you the numbers you should have on the tester.