When I first got my 97 kx250 it took a country mile to stop that thing, replaced the fluid.. that helped a little, rebuilt the master cyl and that ended up just making me gat another used one. Finally took the caliper apart, water got inn and started rusting the piston so it didn't matter how hard you stood on the pedal, the piston was only coming out so far. I cleaned it up and think I put a new o-ring in. Now, it's never been better.
