The rear carb on my race car has an air leak audible at idle that I would like to correct. The leak appears to be around the shaft itself. I pulled the retaining nut and washer off the shaft. The shaft ball bearing fits tightly in its' bore. The diagrams I have all show a "dust cover" of some kind outside the bearing. A spare carb has one. But the carb I'm using doesn't seem to have any room for anything outside of the bearing. My question is....am I missing anything that would be designed to seal the shaft other than the bearing itself. I would assume that re-greasing the bearing might help? Am I missing something?