I have a question about the front brake master cylinder. I have one, but it is not operational. I belive that I have all the pieces, which include the metal piston, 2 rubber pieces (one that is a cup and another that has a hole straight through the middle like a pipe) and a spring. My question has to do with the return valve. I have a propeller looking thin disc of metal, which is attached to the piston (with something that resembles a tack). When I operate the piston it doesn´t draw fluid out of the resevoir, rather it sucks air through the end of the piston. Does this mean that the rubber pieces are shot (turned in the wrong direction?) or am I missing a piece of the piston? Any help would be appreciated.