Carlos,
I recently disassembled my rear brake caliper to clean the seals. I had
thought that the seals had become dirty and the caliper was sucking air
because when I bled the system there was a lot of air in the lines. What I
found was that the seal between the two halves of the caliper had been
compressed so long that it can no longer expand as designed when the
pressure is applied to the caliper. I can see the two halve separate when I
push down on the rear brake lever. No, it isn't something measureable but
enough for air to enter into the system.
I ordered seal kits and pads for the front and rear brakes and intend to
fully rebuild the rear when the kits arrive. I ordered the front kit for
the future. Motorcycle parts keep getting more expensive each year. The
cost of everything was $151.00, shipped to my door. I have found that
Zanotti Motors at http://www.zanottimotor.com/index.html has THE BEST PRICES
for parts.
Good luck resolving your brake problem. Contact me if you need the part
numbers for the seal kits or pads.
Jeff