Motorcycle Repair: Break problems 1983 Kawasaki KZ550 LTD, kawasaki kz550, caliper pistons

Question
I just bought a 1983 Kawasaki KZ550 LTD. While riding it, the front breaks locked up. I had the front caliper rebuilt, put it on and tried to bleed the breaks. However, after about 1.5 hours of bleeding, it seems obvious that air is getting in somewhere. What should be my next step? Rebuild the master cylinder?

Answer
I re-read this question and have your answer, you are bleeding down at the caliper and the master cylinder needs bleeding first.
Bleed the mc at the banjo bolt till no air bubbles come out then go  to the capiper and do the same, this should do it.
P.