rear brakes...comments please

[klingklang]

I just made a search and now my head is full of possibilities.  I need to "pump" my rear brake when I leave the bike for a day or of if I am a very long period without using it.  After, on a regular basis it is ok.   Is it air that is doing that or a problem with the piston?  Never changed a seal on those, only fluids a few times over the years.  Did not had the time to check close yet, too much work, but did not saw any oil leaks.  your comments are welcome

thank you
kk

[nickjtc]

If you have to pump the brakes to make them work and when you do, they do, it suggests that there is possibly air in the system. Low brake fluid level?? If you spin the wheels and hear a constant graunching sound it means that either your pads are worn out (hence the need to pump to get braking) or the pistons are sticking in their bores (hence the need to pump to get braking). If it is only happening after you have left the bike standing for a while it sounds more likely to be air in the system...... More learned chaps than I will chime in on this momentarily.

[JayDub]

worn master cylinder piston seal, Buy a rebuild kit (piston, spring, seals, rubber/s) simple job, follow the w/shop manual .

[PeteH]

 I take it that the sliding caliper pins move freely ?

[nickjtc]

Whether you like it or not, it might be time for a strip down, clean up, and rebuild. Fortunately once you have the appropriate bits and pieces it is not a long or onerous job!

[klingklang]

Thank you guys,  pads are good, level is good. yes nickjtc, only happen when the bike is standing for a while.   Look I have to find time for a rebuild...

[Sin_Tiger]

  most likely master cyl drawing air is most likely. If you're going to overhaul it you might as well do the caliper at the same time, only about £30 more for a full set of seals and rubber boots. Make sure you get the small orifice in the master cyl clear and all the old fluid and crap out of the reservoir and pipes.