I put together a set of forwards with and older PM master cylinder and an Ultima 4 piston caliper for my ‘75 FXE.




After setup it has great pressure and stopping power, and on short rides performs the same every stop.




on longer rides however, i notice that the pedal stiffens up and hardly stops the bike, the little breather hole on the top of the master cylinder cover lets some fluid out, and the caliper/ rotor gets hot enough to start smoking lightly. It doesn’t get red hot but sure hot enough.




the master cylinder doesn’t spit alot of fluid, but when i stop i notice brake fluid droplets that have come out on the top of the cover.




If I let the bike sit for a while, it goes back to normal, strong operation.




Does this sound like an air bleed issue, or a heat iss ue or? Thanks

 

You have to much drag on your pads creating excessive heat this causes the fluid to heat up and expand thus causing the pad to lock up the disk and leak out the MC breather hole.
The fact that it's leaking is the only thing allowing the wheel to turn.

 

would that require another bleed and leaving more give to take up the heat expansion? Or do I need to adjust the pads somehow? Thanks.

 

the rod that operates the master is to long - whats happening is it is as if your foot is always on the brake - I don't see an adjustment on the shaft so - carefully grind off small amounts till you get play between the rod and the master piston an 1/8 inch is all you need - it should be a round end do mimic what you see as an end on the rod

 

^^^Very unlikely, You probably need to rebuild your MC too. The return spring is probably weak and the cap gasket shot.
Then if that doesn't solve the problem you might have to grind down the pads.