CR250 Brakes will not build pressure

Hey Guys,

My bike has been on the repair dock in my back barn for quite some time. Its an 07' CR250. I have been battling with the rear brakes for quite some time. When my bike was apart last year I took the brakes off and they sat for about 4 months on the parts bench. When I went to reinstall them the first time, they would not build pressure at all nor would they push the rear cylinder. So I went and I bled the brakes and that did nothing. I took my brakes off my CR125 and installed them on my 250 just so I could ride the rest of the season. I am back at fighting with them now. I installed brand new rebuild kits on the rear master cylinder and the caliper. The system will now push the cylinder against the pads, but will not build pressure inside the system. I also have a brand new steel braided galfer brake line on the rear. I am out of ideas as to what could be wrong. Any suggestions?

When dealing with hydraulics you have to understand that fluids cannot be compressed and that when pressurized, it is equal in all directions. If there is any air in the system, it will be compressed and you will not build the pressure needed. Unless you did not do a proper rebuild, there is not much more than that.

Only other things I could think of is a bypassing master cylinder or sticking caliper piston. If a brake line is fully bled, it should function the same way as a lever action, but without the bars.

Have the same problem with my front brake, and trust me, I have tried everything bar a few things. (waiting on a syringe so I can back bleed and caliper seals)

There is a lot of very useful info in this thread that I made about my breaks, it is for the front brake however the only thing that differs is the orientation/angle/position of the master and caliper.


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