I've successfully bled my brake lines to remove air several times, each time restoring the proper lever and pedal feel. However, air keeps reentering. I read in a magazine that older blackbirds have o-rings in the master cylinder that dry out, causing this to happen, particularly if the bike isn't ridden much. Sad to say, I haven't been riding much, and my bike is a 1999. I've tightened all the banjo's and fittings to no avail.
(1) Would you agree regarding this likely diagnosis?
(2) Is it possible to only replace the o-rings and not rebuild the entire master cylinder?
(3) Do you know of a source of appropriate parts?
Thanks in advance. -Gary.