Is this with the bike running or just sitting there with the key on? If the latter then that right coil is constantly charging up and getting hot because it's points set is closed. The left coil's point set is open so no current is going into it and charging it up. So, basically there's nothing wrong, it's how the system works. But obviously, it's not a good idea to let it happen. Don't let the bike sit there for long periods of time with the key on but not running. One or the other coil will get very hot if it's points set is closed.