Bleeding the hydraulic brakes

If present, remove right saddlebag.
Remove the rear master cylinder reservoir cap. As the pistons are pushed back into the caliper, fluid level may rise more than 1/8 in. (3.2 mm). You may have to remove fluid to allow for this.
Loosen, but do not remove, both pad pins (12 pt/0.25 in.).
Pry the inside pad back. Use steady pressure to prevent scoring the brake disc. Pry between the pad and the brake disc in order to push the caliper pistons back into their bores.
Once the pistons have been fully retracted into their bores, pull pad pins part way until the inside pads drop free. Note the pad's original orientation for replacement purposes.
Install pad with two tabs on the inboard side of the rear caliper.
Install new inside brake pad using the same orientation as the pad previously removed. Curved portion of pad must face upward.
Install pad pins until the pins snap into place with an audible click. Do not fully tighten at this time.
Pump brake pedal lever to move inside pistons out until they contact inside brake pads.
Pry the outside pad back. Pry between the pad and the brake disc in order to push the caliper pistons back into their bores.
Verify that inside pads are captured between brake disc and pistons. Completely remove pad pins to free outside brake pad. Note the pad's original orientation for replacement purposes.
Install new outside brake pad using the same orientation as the pad previously removed. If the inside pad moved during the previous step, reinstall. Curved portion of pad must face upward.
Install both pad pins through holes in inner and outer
brake pads. Tighten to 180-200 in-lbs (20.3-22.6 Nm).

Push the caliper pistons fully in.Pour fluid from the top and watch it always so it never runs out of fluid during the procedure.Turn the bleeder on the caliper counterclockwise 3/4 of a turn.Have a tube attached on the bleeder with its other end in a bottle.Press the lever once all the way in. Hold it pressed.Close the bleederRelease the leverRepeat until no air bubbles comes out of the bleeder.You should already feel a little pressure on the lever.Now start pushing the lever 10 times (pressing the master cylinder) and on the last one, hold the lever in and open the bleeder. Close the bleeder and release the lever.Repeat that until no air bubbles comes out of the bleeder.At this point you should be ready to ride.If you still don't have pressure on your lever, you need to take the brake master cylinder apart for repair.

If the piston was not compressed completely back into caliper, ( I use a large C-clamp,) then the caliper/brake pads will not fit over the Rotor. Also when you compress the piston back into the caliper be sure the brake fluid resevoir doesn't overflow when the fluid returns during the compression process.

If you do not have the correct compressor, you can use a C clamp. Use the old brake pad as a spacer, and to be sure to compress the piston squarely.

Watch the fluid on the master cylinder. If it was topped up, you will force fluid out and on to your paint and other items under the hood, NOT GOOD. Stated another way, a set of brake pads consumes almost a full master cylinder (reservoir) of fluid. When you put in new pads, and compress the pistons, all of that fluid goes back to the reservior. Drain off to keep fluid from spilling.

By the way, something NOT so obvious is: as you know a pressure will go to the point of the least resistance. That may be the other caliper, if you have it off the rotor. You can sometimes push the other calpier piston totally OUT. Do one caliper at a time, leave the others installed, and no worries.

As the break pads wear it creates a greater volume(capacity) at the caliper piston/s.This causes the fluid in the reseviour to go down.(even though you have no leak) then you top it up & it will again reduce fluid level as the pads wear further.When the pads are replaced you are required to push the pistons back in to accomadate the new(thicker) pads. Before you push the caliper pistons in at brake pad change you will need to drain out some fluid(from the resivour) to stop the resivour from overflowing. This is typical of all hydrolic braking systems on both bikes & cars.Check the pads, If they are wearing this symptom is compleatly normal.