Motorcycle Repair: Motor backfires, harley xlh, 2o minutes

Question
I have 1975 Harley XLH Sportster. After I ride it about 2o minutes it starts to miss and backfire. If I let set for a few minutes, it starts up like nothing happened until it gets hot again then starts missing. Any ideas?  

Answer
There are several things that can cause this problem. Coil, plug wires, jet plugged in carb. You never said if you have points or electronic ignition. If you have points the points and condenser could be bad, or if you have electronic the pickup could be bad.
You can test the coil and plug wires. If you need to know how let me know.
If they test ok I would then go to the points and replace them as well as the condenser. If it still has the problem then pull the carb and check it for dirt.
Good luck and happy riding
Mike