Motorcycle Repair: spark plugs and idle set, couple of days, harley

Question
I have a 1977 Harley 1200 Sportster. Bike has been sitting in garage for 2 years, very good condition, i ran it for 2 days smooth running. On the thrid say i broke down. i pulled the plugs and they were blackened. Oil is running very rich,so i tried new sprk plugs and it didnt work. when i press the started button it is very weak. I pulled , charged and tested the battery it is fine. I got it started down a hill the other day and it backfired.  

Answer
If your plugs are getting fouled then you either have a carb problem or an ignition problem. Since you ran it for a couple of days without problems, then I would say an ignition problem. test your coil. You might have a weak one.
Good luck and happy riding
Mike