Just because your spark looks good does not mean it is. Put a new plug in (they are pretty cheap) and I would maybe try swapping the rear coils. You may have a higher rpm miss that could be one of many electrical issues, or you could have something wrong with your carbs. Do you notice this problem at certain rpms or speeds while on the road? Or can you feel it miss? There are other guys that are a lot more carb-savy than I am, but it seems like most of us with carb problems are from things plugging up our carb causing it to run lean... that is what makes me lean more towards a spark issue (could be wires, coil, ignition, plug). I try to avoid breaking into the carbs as much as possible, but they aren't too bad to play with either.
Did this problem just start? How many miles have you put on the bike? As godsend1 said, could be a needle/seat/float problem too. One way to check that is to make sure your carb bowls are full of fuel, take off the main fuel line and blow into it and then check to see if fuel is leaking out anywhere.
Good luck!
Jeff
