hi everyone. I've just fitted a new back brake pipe on my 2012 gasgas txt pro. I've been bleeding the brake. you know. the usual undo, push, tighten, release method. after an hour or two of doin this the fluid stopped going down in the reservoir and no bubbles were coming out, and when i released the nipple,  and pushed down on the Lever, fluid started to come out of the nipple and still no back brake is working. this is my first time bleeding brakes. any suggestions?

Remove the brake lever and use a phillips screw driver or balled allan wrench to pump. Sometimes Burping the banjo bolt to the M/C helps get it started. Having the caliper higher than the M/c helps the air to flow out. I like using a 3 foot clear hose straight over the rear fender.

I feel your pain, can be a difficult and frustrating task. Here are some suggestions based on what I wrote down last time I had trouble bleeding the rear on my 2010.  

-Try cracking open the banjo bolt open (while you are holding the pedal down).

-Try pushing in pistons all the way, blocking them from extending out by inserting old pads or wood shins, then try bleeding

-Try "reverse" bleeding using syringe. Do this BOTH from the caliper bleed nipple and at the master cylinder.

-Put rear end up on tail gate, used screw driver to pump Master Cylinder

Hope this helps!
 

Syringe

Good advice on methods in the posts above, but i find a vacuum bleeder the easiest method.

For any method wraping a little ptfe tape round the bleed nipple threads can help, just avoid the taper where it seals.