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GS750 - rear brake bleed issue after caliper rebuild

  • Thread starter Thread starter tc80211
  • Start date Start date
T

tc80211

Guest
Hey guys,

'81 GS750 - noticed a bit of "grinding" sound and come to find out only the inside piston has been actuating on my rear brake. Take fully apart, buy and build with new seals. Reassemble and put back on back.

To bleed I use the inside bleeder valve first and do the brake lever pump bleed method. Pedal gets stiff with only about 1inch of play and wheel is now completely locked. No spin whatsoever. It appear the piston auctuated out but is not traveling back in when pedal is released...

Thinking I must have missed something. MC pushrod adjustment? Hell, MC rebuild? Or just need to have piston bores honed?

Any thoughts would be awesome.
 
Sounds like your brake piston is stuck.
I'd attach a hose to the bleeder and loosen it slowly. With the pressure off see if the brake loosens it's grip. If it doesn't I would pump the brake and see if fluid is indeed pumping. If it does I would think the master cylinder is working and you need to look at the brake.
 
even with bleeder open, brake does not loosen. I can open bleeder and pump brake, fluid flows fine into the can below.

So maybe the piston bores just need to be more thoroughly cleaned? I can push each piston in by hand, although its not smooth and does take alot of pressure.
 
If the piston bores are clean in the caliper I'd clean out the master cylinder. There is a return port that gets clogged easily.
 
Thanks guys, I will give the master cylinder a look after work today!
 
Master cylinder cleaned out... bakes back on... Bled as they should be... still locking up...

However one thing I also tried was bleeding the brakes will not on the bike, with just an old brake pad in between the pistons... and I noticed they actuated correctly and released as they should... however the pistons are much further extended then when pads are installed and attached to bike... So kinda stumped at this point... Just trash em? Go buy replacement somewhere?
 
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