I replaced the brake line that goes from the master cylinder to the ABS junction in preparation for 3.5" handlebar risers. I bled the front right brake completely and some on the front left before swapping to the extended brake line. I started working on the rear and after pulling a fair amount of brake fluid, am getting nothing but air. It's worth nothing that I've kept the MC reservoir full (after the brake line exchange), and and the pressure on the brake bleeder gauge shows a steady decline in pressure when I try to take fluid out, making me think it's sucking air out. Any idea what is going on?