If the breaks are working when pumped and no fluid is leaking out, it is a classic sign of air in the system. How it got there?????? Maybe the pads wore and there was not enough fluid in the reservoir to take up the extra volume.
The problem is the damn rear link lines. They run from the rear reservoir up along the right side of the frame, down to the splitter branching to the two front calipers. Also the secondary master cylinder line runs back on the left side of the frame to the proportional valve and then drops down along side the right side swing arm to the rear caliper. You have to push a lot of fluid around the bike to bleed it properly.
I had a yellowish fluid originally and blead with a clear. That way I knew I had pushed the new stuff all the way.

 

I had the same problem with my old Hyosung GT650... in my case the problem was the moron at the wheel.

I'd gone wide in a corner about three weeks before and ended up on my side in a ditch full of muddy water... thought I'd escaped with damage only to my pride.

The part of the story you'd be interested in was that the muffler had been pushed towards the bike and bumped the rear brake calliper when the suspension was doing it's thing. The rear brake would come back after a few pumps but did nothing the first times... turns out the pumping realigns the brake housing.

Make sure there is room between your exhaust and the brake/swingarm at full compression and check your memory to see if you've had any equivalent sloppy encounters... (that's funny hey)

 

Thanks for all your help guys - much appreciated!

Turns out that in the end,the rear master cylinder brake fluid resovoir cap was not screwing down properly and not creating a proper seal......

Also the feed pipe for the resovoir possibly had a split in it too,so went to the local breakers and got a replacement (off a blackbird but still the same!)

Rear brake is working fine now which i'm pleased about,trouble is the front brakes are binding quite a bit (they were before the problem with the rear)

Any of you know any good tips for freeing off the callipers on the front? We've already stripped down the callipers and cleaned up the three pistons on both of them.

Ain't made any difference and i'm not sure whether the problem is hydraulic or mechanical.....................

 

Are the fronts binding (staying on when the lever is released) or just uneven breaking?
Maybe they are glazed over. In that cass you can take emery paper and de-glaze the rotors and some sandpaper to de-glaze the pads.

 

Yeah,they are staying on when the lever is released on the front callipers.......the pads themselves have worn evenly and don't appear to be glazed.

We've already taken the sheen off the pads,the front callipers do realease when i gave each one a few light taps with a rubber mallet.

I don't know whether the problem is hydraulic or not........but it's not a slight bind,the discs are still being gripped pretty tight when the front lever is
released......[:@]

 

It sounds like the pistons are sticking. Have you removed them from the calipers?

Remember one thing, the lever works the two outer pistons in the caliper, that's it. Just like any other bike without LBS.

If you have not removed them, you should pull them and clean them. I used a shop rag and pump pliers to pull mine while slowly rotating the piston.

When you put them back togeather you only have to bleed the upper valves.

When the calipers are off the bike do not press the foot pedel or the center pistons will be activated.

 

Hey BTW, I pull one side at a time with the front wheel on. You will have the clearance to get the caliper off with the front wheel in place. It is easier to put them back on that way vs trying to slide both rotors in at once.