my bike was doing something similar. i had a VERY weak spark the only time i could see it was in a dark garage. I took the wiring harness off, shortened it, pulled off all the butt connectors that the yahoo before me had on there, made sure all the connections were soldered good, and taped it up. BEAUTIFUL spark now. from expierence, will knock the s#$t out of ya. IMO its in the wiring like the above posts said
Jim