Rear Brake Binding Your views?

RPMDAKAR

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2005 Dakar ABS 70K + had a very difficult life before landing in my garage, latest tribulation being a rear binding brake, so extreme the rear disc has warped warenting replacement. I am at present using a spare rear wheel & disc and my first trip out was a relevation, bike so much better, more willing and a joy to ride until I applied the rear brake, immediatly it returned to its former self, with the rear brake binding and APITA to ride, this was after my servicing the rear caliper and replacing the rear pads. So, its back on the bench, with a rock hard pedal, and needing a good sort out. My initial reactions are that the rear brake hose could be mullered and not allowing the fluid easy return when the pedal is released. I am appealing to the informed here, just in case I am missing something more obvious, all ideas gratefully appreciated.
 
That's a definite possibility as I have had to change 4 rear hoses for folks that we eventually tracked down as de-laminating and acting as a one way valve holding the rear brake on

Actually only the first one was irritating to track down and in the end difficult to believe had happened so far 4 in 10 years isnt bad :rob

Also are the slides free moving and can you slide the pistons back in with thumb pressure only? (<- Sorry to ask silly question but I've No idea of your technical knowledge)
 
Very common on these bikes.

Fit a new master cylinder and it should cure it.
There's a nylon bush inside and corrosion can form behind it causing it to bind.
 
Had similar with mine a few years ago and it was the master cylinder. Have a look here it might help.
 
This Dakar has been abused badly by a so called "Bike Shop" & previous naive owner who spent good money having bad work done. When I serviced the rear caliper it was really gunked up so I used a G clamp to assist the piston to return prior to fititng new pads, as far as I am aware (until I get into the garage) all was as it should be when I replaced the caliper & wheel. As for Tecnical knowlege, hows about flying out to Chile to rebuild a R80g/s after a massive write off? Google Cynthia Milton. I have experienced the same symptoms on older /6 bikes and braided hoses cured the problem. Thanks for the reply
 
As above, really common and usually the rear master cylinder. You can buy a rebuild kit for it if you don't want to buy a new one.
 
When I serviced the rear caliper it was really gunked up so I used a G clamp to assist the piston to return prior to fititng new pads, as far as I am aware (until I get into the garage) all was as it should be when I replaced the caliper & wheel.

If that was calliper off the bike and no hose? They are too tight!

The beauty of these bikes is their simplicity (relative) Like airheads

all the parts are available for that rear brake

Rear Slide Rubber Kit Link


Rear calliper pad pin kit BRA51955

Rear brake caliper repair kit | BRA51957

Caliper repair kit with piston rear | BRA51959

And just for good measure

rear master cylinder full overhaul kit | BRA36241 NB 11MM bore

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Now have no bake brake at all!

Following my OP regarding this basket case of a bike, I went out for a quick test ride after getting it out of my garage and it all moving freely, only to have the back brake bind on so badly within half a mile the whoe system was smoking and I now have nothing on the footbrake at all! So, I will replace both the Master Cylinder & Rear flexi hose as a matter of course. Thanks to all who responded.
 
Check your disc hasn't gone blue and the caliper pistons haven't melted, that's what often happens :)
 
Sounds to me like corrosion behind the piston seals, which 'push' the seals out of their seating and cause them to grip too tightly around the pistons, in turn stopping them from retracting freely. Used to get this all the bloody time on my Tiger - especially on the rear. Cure (obviously!) is to strip the calliper, clean out the corrosion and general grot in the seal seating moat, fit new seals, clean/polish or replace pistons, reassemble. Dremel with a thin brass wheel is an excellent means of cleaning the moats out.

That would be my 'non-bike-specific' diagnosis anyway.
 
Been advised that new Master Cylinder & Braided hose will be here in the morning, so armed with good intention the M Cylider as duly removed, white plastic collar seized solid in its bore and the main seal looked very sorry for itself, also noticed a slight grove between the supply and pressure galleries. Started to remove the rear brake pipe, no probs with thecaliper end but absolutely no joy at the other end onto the metal pipe, so hoping the new master cylider cures my problem or else the whole back end of the bike has to come apart to access the shagged bolt!!!! Not on my to do list!
Just to explain, the caliper was given a going over when the S/H rear wheel was used as a replacement along with new pads.
We shall see if a cure is at hand?
 


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