Honda rebel running very rich, how to fix it?

First, make sure your air cleaner is not plugged or dirty. This will cause a rich mixture. Next make sure the choke is completely off when bike is running. Gas is not leaking past the choke plunger seal. If the mixture needs to be adjusted , it is the screw under neath the carburetor, up front by the intake manifold. Before making any adjustments, count the number of turns IN, before the air screw seats lightly. This should be the factory setting. Call a dealer and find out what the standard setting should be. Start there and make minor adjustments(1/8 turns) till you get the spark plug color you desire.