master cylinders 101

[kar_the_terrible]

Hi,
Does anybody know the exact flow path for brake fluid in a master cylinder (Im assuminig all are basically the same) FYI, single piston floating caliper.

The reason im asking is that if I knnow how the fluid flows, I will have a better idea of diagnosing why my rear caliper drags thus robbing me of handling, power and pads.

I've checked and rechecked everything, new seals in the calipers... yes thay are seated correctly. New seals in the master cylinder. The brake line apparently is fine and not collapsed (although this is one of the suspects).

*BUT* I couldnt find a reliable rebuild kit for 79 xs400, and hence decided to fab my own master cylinder piston... by joining together the base of a yamaha m/c piston, and the top of another with a 16mm bore as is required on mine. End result was that I had a piston that was one solid rigid unit, whose base sat correctly, but was about 4mm longer. I did ensure that I have enough travel distance in the m/c, and to the best of my abilities try to see that no holes were blocked or opened up.

Now I know that this is probably the reason why fluid doesnt flow back reliably in the m/c chamber, but I'd like to be sure before I shell out $55 to a dealer for a spring and few rubber seals.

Oh another thing.... the OEM number on the part I need is 1U4-W0042-50-00, and the rear m/c rebuild kit on an xs750/800 is 1J3-W0042-50-00, does that mean they cross reference? anyone know how to read yamaha part nos. ?

[kar_the_terrible]

Nevermind, they do not match.