Hey guys, having trouble with my rear brake caliper. When appllying the rear brake, the foot control pedal goes all the way forward without applying a great deal of pressure while riding. Pumping the pedal a few times before braking achives nothing. Plenty of fluid, brake pads seem okay, no leaks, was working great. What's going on?

 

Best thing to do as it a safety feature is to give it the once over. Pull the cap to check fluid level, to make sure it has enough fluid. The sight glass is an indicator you have fluid, but does not tell you if its full
cause as the level drops, the rubber seal inside drops accordingly to minimise the contact with air. Your fluid level can be low, and still read full in the sight glass.
Bleed the brakes to eliminate the possibility of any air that may be in there, even if you can't work out how it could get there.
Make sure the pins and sliders are not seized on the caliper. With the pads out you should be able to move the caliper easily sideways with your hand, or take caliper of and pull pins out clean, re lube etc.
Make sure the piston is not seized in the bore of the caliper. Again it should move in and out of the bore when applying the brake by hand and the caliper off. Retract the piston using a brake piston clamp or similar. If it feels really tight and will not go in or out, then it is seized and you may have to soak it in penetrine or similar and try pump it out with a hydraulic enerpac hand pump unit. 
Often, a simple G clamp does the trick. You may have to do this with the cap off and fluid level low so when you retract the piston, you can see the level rising and you won't overflow it everywhere.
If you have ABS, then it may have air in that system and you will need to find out how to get air out of that as i don't know.

Hope this helps Crazy man.

Cheers Hutch.

Before you do all that lift ya back wheel and spin it and see if ya disc is bent or warpped.

it will spread ya pads open giving the feeling that there is no brakes and that you have to pump the pedal to get them to grab

torn seal/oring in the master which will not allow pressure to build and is bypassing in the master or as above not enough fluid which will make them feel spongy
normally a bent/warped disc brakes will still work fine but you will get a pulsation thourgh the peddle / leaver

Cheers guys, all good info, I have checked all the above, bare the master cylinder, & I am leaning towards fucked rubber seals & rubber, might take it to a HD Pro for an opionion before I pull it apart! Thanks again! C.E. " src="/DesktopModules/NTForums/themes/_default/emoticons/smile.gif" />