Is it the blue head 80rv or one of the others? Do you have a picture of your installation/baffling? The ZDZs seem to require more attention to proper cooling than others to meet its basic cooling needs, and it doesn't take too much hot running to ruin your cylinder. You'll find the bore to no longer be 'true', and even a light scoring of the bore and new ring will be useless. Do you have any pictures of the piston skirt through the exhaust port? Have you pulled the cylinder and checked if the ring is stuck or beginning to?