[tbirdtbird]

well when u are cranking do you get the blue spark I mentioned?

Resounding backfires are either wrong timing which is prolly not the case since it just ran on the road OK, or very lean, not getting fuel. loosen the fuel line nut on the carb and pull back on the line, be sure you have 1/4 inch between the end of the tubing and the inside back wall of the carb.