[cjriddle22]

I bought this rig about a year ago, front and rear brakes were non-existent when I purchased it. Ended up completely replacing both discs and pads up front (and did a complete rear drum rebuild). Did a full bleed and everything seemed good to go, but if I ride for more than 10-15 minutes the front brake lever starts progressively getting harder and harder (like the fluid is getting warm and starts expanding). Then it gets so hard that the brakes start applying themselves and the front tires eventually lock up. It builds up so much pressure that if I crack the bleeder valve it squirts brake fluid like a geyser, so when I am riding I usually keep an 8mm box wrench with me and just crack it as it starts getting stiff and that buys me more time. I feel like its not letting the fluid back into the reservoir. I didn't have this problem before I replaced the discs and pads (was super soft and squishy, def had air/water in the fluid). Probably should have just did a good bleed before I replaced parts, but I tend to overkill and just start replacing things just because I wanted to "make sure" it was done right.

Do you think the master cylinder needs to be rebuilt? Or is there another common problem I should be looking for before I tear it all down?

 

[retro]

Yeah, the outer cup seal in the master cylinder may have swelled (due to improper fluid added) and is blocking the return port, OR, the tiny fluid return port has become plugged up with grit/corrosion.