are they interrupter bar brakes or road levers? cantilever mount? first crank the spring tension on both sides so they have maximum pressure. the posts could be mushroomed, so filing them down to round shape is first step if they stick without the cable attached. then when sufficient tension is achieved, hook cable up and pull lever. if one side dosen't return crank up tension or decrease tension on other side. that should center. more tension overall will help with poor feel at lever. i'm not a huge gan of canti brakes v-style are better nowadays more options. avid still makes the shorty4 canti which is as good as they get probably. let me know if this helps. more info needed if it dosen't. later!