Be careful on the back piston, it is part of the parking brake ass'y. To get the piston back in to fit new brake pads you need to screw it in, not just press it back in. I forget which way to turn it. It has to do with the parking brake. There are all kinds of little pieces inside the piston. It has a big cross hatch on it and I used a piece of 3/16 flat stock to turn it.
If changing or bleeding brakes on the back (left grip) bleed the front first piston (the middle part of front brake, lower bleeder)then the back piston.
DO NOT ALLOW RES TO GET LOW!!!!!!!!!!!!! It is a pain to get the air out of the lines then. Usually an air bubble gets caught in the banjo bolt at the handlebars.
Hope this helps