hey man im pretty new to this site and the banshee, but i had this same problem with my banshee, it would only start with a prime through the plugs and wouldn't idle after i let off the gas, and the choke tube that connects both carbs were missing, i replaced it and adjusted the idle screw and she fired up and ran perfect,, but mine never had the same spark issue as yours,,, hope you get her runnin right dude,, best of luck!!