back brakes seized up? HELP

[mooml]

Not knowing much mechanically about my bike I took it into a mechanic for its 24k service.  Back brake pads and all fluids were replaced as well as numerous other things. About 200 miles go by after getting it back and everything was running better then when I bought it.  Then the other day I was cruising at about 80 on the interstate and the bike started to slow down extremely quickly.  I pulled in the clutch and put it in neutral but it continued to slow until i was able to get onto the shoulder and inspect things.  I noticed that there was sediment like junk on the back rotor and the back brake was not working at all.  I could push the lever down but there was no braking ability or resistance.  I let it sit for a few minutes and decided to try to get home which was within a few miles and now the bike seemed to work fine mechanically but I continued to have no back brake.  After getting it back to the shop a different mechanic (the original was out of town) looked at it and noticed that there was no brake pad left at all and he thought the stuff on the rotor were pieces of the pads.  I am currently waiting for the original mechanic to look at it since he is the head mech and shop owner.  I have been extremely frustrated with the whole situation since I just spent $1400 on maintenance and came very close to going down at high speed and just wanted to get some unbiased opinions on the situation before calling the mechanic back.  Mainly I'm looking for opinions on what could have caused this and whether or not I should hold the shop accountable.  Leading up to the incident the bike had been sitting for 6 hrs in 70-90 degree heat but had worked fine before that.  Also I was not using the back brake at all in the moments before or during the incident nor had I done anything but put gas into the tank since I got it back.

[Howie]

Could be the mechanic's fault.  Or not.  You will probably never know.  Overfull reservoir or pedal free adjustment could cause this.  So could the piston refusing to retract due to muck inside the cylinder the mechanic wouldn't be able to see or just coincidence.  Both pads were gone?

[brad black]

two in one day!  rear brake pedal clearance/freeplay, as in not enough, is the cause of this in my experience.  the master cylinder piston has to be able to fully retract and then there also needs to be freeplay between the piston and pedal pushrod at this point.

if someone has played with the pedal freeplay or pedal position then yes, it is their fault.  make sure all the nuts on the adjusters are tight too.

[han711]

Ya same experience haha. Gonna have to ride my bike in real careful to the dealership this Tues. Oh well live and learn!

[mooml]

Thanks for the posts.  I forgot to mention that about a year ago I put the bike down in a low speed accident and the back brake lever got bent about half way along the shaft.  I probably put another 1k miles on it before getting it serviced but other then cosmetically I never had an issue but asked the mechanic to try and straighten it out while it was there. Could the accident or straightening out of the lever have caused the free play to get thrown off and if that is the case shouldn't they have adjusted this when they reinstalled it?  Would I be better off ordering a replacement part? 

[han711]

Had the same issue. I got mine replaced cuz after a bit of riding it'll eventually crakc on u mid ride and that's no fun lol. Look at it as an opportunity for new parts

[H-2 CHARLIE]

bleed the brake and leave extra play in the lever . I had the same  problem and this cured it .