Ignition Coil Overheating

There are some new suggestions which I appreciate. There were several questions that I can answer. First I measured the resistance of the ballast resistor warm but not hot. Second I have checked and there is gas but no/weak spark after the engine quits. Things have to cool down before I can start it up again and when cool it fires quickly and is ready for the races. My problem is that I have to get to the races within 10-15 minutes.