[Closed] Brake Problem (M575s)

Just built my Inbred, but the front brake pulls to the bar. If I swing the bike up on end and pump the level it comes firm, but it is only a few minutes before its pulling to the bar again. I can pump it a little as I ride, but clearly would like a more permanent fix. It doesn't seem like a 'bleed' problem, as it is firm enough when pumped. I am leaning towards some sort of leak in the master piston seals, but would like the collectives combined wisdom before I get on to On One about the issue.

Cheers for all your helpful answers.