2010 Front Brake Issue

Just picked up a 2010 YZ450 with 70 hrs on it. It is in good shap excpt for front brake.

It have an 08 master cylinder on it. Was trying to diagnose issue but no luck. The front barke will grab partially but as you hold it, it releases.

I tried to bleed the brakes but still no luck. I then took apart the master cylinder, cleaned it up. All seals and spring seem to be ok.

Still behaving the same way.


Any suggestions as to what to try next?




Sounds like air in the line...did you remove everything and bleed it on a bench? Sometimes if you unbolt everything it's easier to bleed and see what is going on.

If the brake feels "normal" at first, but pulls to the bar if you hold it long enough, fluid is leaking past the master cylinder piston internally.  Rebuild it, or replace it if you don't see any external leaks elsewhere.

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