When I stripped down my old caliper I remember there was a check valve that fitted into the large spring inside the master cylinder. I ordered a new re-build kit many moons ago and foolishly junked the old master cylinder parts. When I went to re-build the master I found there was no check valve for the spring, thinking I had lost it I ordered a new master cylinder kit but in the new kit there is no check valve either.
I tried using it without the check valve but found that I good get decent pressure on the lever after bleeding, but the pistons seem to retract into the caliper when the lever is released, this means that the lever is nearly back at the handgrip under braking. I assume that the check valve acts a little like a non re-return valve and stops the pistons from retracting so much when the lever is released. Has anyone succesfully used a master cylinder without the check valve?
