Why does air and oil leak from your rocker boxes when gaskets are new on a 1991 Fat Boy?

If the air & oil are coming from between the three "sandwiched" rocker box layers, it can only mean the rubber gaskets were installed improperly. They must be replaced and installed correctly.

Don't be tempted to glue the new gaskets in place with silicone. This can allow dried silicone to break loose and clog internal oil passages, possibly destroying the motor.