something i was told just recently when my bike was playing up was to check the lower coil for high rev spark

what the person did was removed the cap of the bottom coil, held it with plastic pliers near the sparkplug, started the bike and revved it out over 7k and would see if the coil would still spark at those rpms

he said it was something to do with the bike having a high rev spark or something i cant remember... but something on those lines.. no harm in trying it though