Hi all you GS'ers, here's a new question for ya. I was bleeding my front brake, and got a bit carried away thinking I could do it in one easy step. Before I know it the fluid starts backflowing into the line with loads of air. I look up and there is my master cylinder, empty  
Now I've lost pressure in my line, is there anyway I can manually gain it? Or do I need aftermarket tools/peripherals? If the latter, which tools do I need and how are they operated.
Thanks Simon

Did you look under the seat?


JK
OK You don't need any specal tools (but they are nice to have). About all you really need is a bit of 3/8 tubing, preferably clear. Put it over the bleeder nipple (hehe he said nipple).
Fill the master resivour with fluid and keep it at least half full at all times (that was your mistake). Otherwise you will suck air into the system and have to start all over.
With the brake lever squeezed, crack open the bleeder on the caliper. Some fluid should come out. And the resistance on the lever should ease and you can squeese the lever to the bar. BEFORE it gets all the way and you have to let go, retighten the bleeder. THe way these work is that sqeezeing pushes fluid into the system, but releasing draws more in. If you don't have the bleeder closed, you will suck air back into the caliper.
Anyway, hopefully some bubbles came out. If you do this a couple of time and no bubbles come out.  The air may be trapped in the upper part of the line. If so you are going to have to crack the upper banjo fitting.  To do this, wrap a rag around the line and the end of the master cylinder. Put pressure on the lever and slightly loosen the top banjo bolt. Fluid and air should ooze out but it might squirt if there are air bubbles. Again retighten the bolt BEFORE you let go of the lever!

You should feel the brake lever get tighter and tighter as you release the air.

good luck.

Sorry let me explain myself a bit better. I was using about 10" of tubing with a valve on the end so no air can re-enter the system. I was happily bleeding, using the "pump to handlebar then close" technique, but the fluid in the cylinder ran out. So i was effectively pumping air, via the cylinder, into the line. Well, I filled the cylinder back up with fluid and tried to pump again, but now the brake level just moves with no tension at all. So there is no way I can pump any of the air out.
Knowing this, will the same technique you spoke of, involving undoing the  banjo connector, still work?
Thanks Simon

Yeah, You have basically "vapor locked" the master cylinder piston.  You need to get the air out of the top of the line before it will refill with fluid.