How hard are you pushing the brake pedal? Honda's rear drum brake setup isn't hydraulic, so you have to push pretty hard on the pedal. Another problem could be mud or water inside the brake drum assembly. If you're getting a hard pedal, moving the brake arm backwards won't really help any. To be honest, Honda doesn't have the best rear brakes. I have never been able to keep good drum brakes on the rear of a Honda, even when the shoes are new. They will usually stop you, but you have to push them real hard. Sometimes you can get them to lock up and sometimes not. If you haven't already, you could try disassembling the brakes and cleaning everything good and it might help.