Hoppedup made a good point, if it'll fire by putting your hand over the carb it might not be electrical. I'd start w a leakdown to check for /eliminate leaks, than put an inline spark tester on the non firing side, how have you checked for spark? Just because that side doesn't fire dosent always mean there's no spark. You could just be getting too much fuel on that side. I just had The same issue w mine and it turned out the carbs werent quite in sync and air screws were at like 1/2 and 4 turns out