I have a 07 Ultra Classic that I didn't ride for about 6 weeks, too damn hot to ride here is TX. I took it out and my rear brakes only had a little stopping power. The pads are good so I replaced the brake fluid which was dirty and that didn't fix the problem. Is there a way to know if it's the Master Cylinder or the caliper?


Thanks

 

a leaky master cylinder will make pressure ( like when you come to a stop), then slowly bleed down as you sit there with your foot on the pedal...there may not be any fluid leak- it could be leaking internally past the seals.



mike

 

If the caliper was binding to the point that you had to exert more pressure in order to stop, it would stay in a bind and drag. If you are stopped and rest your foot on the brake and it slowly sags down, it would be the master internal leakage(assuming no external leak). If it has a spongy pedal and requires more than normal pressure in order to stop, you have air in the lines and need to bleed the system. I have seen flexible lines break down and get balloony without leaking and give the spongy feeling also.

 

There's little pressure anytime, the pedal just goes to the bottom with little resistance or stopping power.

 

If your positive any air in system has been bled out,it sounds as if your master cylinder needs replaced.

 

Assuming it was working fine and you didn't do anything to the system, I will say you have internal bleed-by in the master. Replace it.

 

You could rebuild it.
42382-87E
REPAIR KIT master cylinder | FB/FC/FF/FR/FS/FV/FY/KB
$62.12

 

I bled the brakes after this started and it didn't help so it does look like the master. Thanks for all the input.

 

Woah there! Don't go spending any money just yet. You say your rear brake doesn't have much stopping power, do you mean the pedal is spongy, or firm? If spongy you probably have an air bubble, if firm you may have a caliper problem. That could be the pads are hanging up or one or more pistons are sticking. I suggest removing the caliper and cleaning it, checking that all pistons move and that the pads are free to move. I have one bike (different brand) that routinely clogs up with brake dust and binds the pads.

 

The pedal goes easily to the bottom and minimal braking. I bled the brakes just in case there was a bubble and that didn't help.