Yup, you need to bleed them. Most Avids have a air bubble in the master cyl and when the bike is hung up the air sits just in the right spot for it to get into the wrong part of the system. You might be able to back bleed it by pushing your pistons in and forcing the bubble back into the master cyl. But the best thing to do is to bleed them with fresh DOT5.1 fluid. DOT 4 is ok but 5.1 holds up better.