My 2013 B5 had the same problem. Actually a lot of problems. You had to push the pedal way down to get anything, it would slow the bike a little bit, but also made a loud scrubbing noise. I took it all apart, and found that only one shoe was contacting the drum. That shoe and the drum were glazed. I removed the shoes, cleaned them with brake parts cleaner, and sanded them. I did the same thing with the drum. Like most rear drum brakes, the Bullet has a single leading shoe design with a single cam. The pivot point of the cam can be adjusted (I've never seen this before on any other bike) and it was off. I centered the brakes with the unit off the bike, by using the actuating arm by hand, and putting pieces of paper between the shoes and drum to get both sides even. It now works fairly well. More than well enough for a rear brake. And the scrubbing sound, which was most likely caused by glazing, is gone. I also adjusted by tightening the nut on the rod till I could feel drag on the rear wheel, then backed off until the drag just stopped, and the wheel spun freely.