I have a craftsman ch which I have ainsaw,done some work on(replaced gas tank and fuel lines) and I had it running and adjusting the carberater when it stopped and locked up. I wasn't able to pull the starter cord. I took the spark plug out and got it unlocked. Now it will not start. It seems like the piston rings to me. What are your thoughts on this because I prefer to do the work myself. Thanks for the help!