Hello, I have a 1990 banshee that was freshly rebuilt, it has fmf pipes and proper jetting, it had some spark issues but we found out the key switch went bad. it now starts up and idles, sometimes other times it will back fire when you kick it. But once it is idling it sounds fine until you hit the gas and then its bogs down, we are messing with the timing. but to be completely honestly im clueless what could be causing it ,the carbs are in time and clean, any ideas would really appreciate it.