rear brakes wont work after master cyl rebuild

[k100kiwi]

hi everyone,looking for some advice.my 91 k100rs.ive put a new kit in and cant find any leaks,but still no brakes,new lines,fluid is getting thru to banjo bolt on caliper end,but no further.removed disc unit,blew air thru,reconnected,still no brake.any thoughts welcome.Martin.

[Martin]

You probably still have air in the caliper. How did you bleed them, I've found that vacuum bleeding is the easiest & the best way. If you can't vacuum bleed, then you pump the brake pedal 4 to 5 times, then while holding the pedal down crack the bleed nipple to which you have attached a piece of clear tubing. Run the tubing into a clear glass jar with a small amount of brake fluid in the bottom and submerge the end of the tube in the fluid. At first you might  not see any fluid but  do up the nipple, pump the pedal again hold down the pedal undo nipple, tighten nipple & repeat. eventually you will see fluid with air in it. Keep on repeating the process until you don't see any air in the tubing. Keep the reservoir topped up, if you don't you will reintroduce air and you will have to start over. Once you have expelled all the air you should have a firm pedal.
Regards Martin

[Inge K.]

Is the pedal properly adjusted, it should be a small play between the pedal and piston.
If the adjuster is to close to the piston (ie. pushing it just a hair) the piston won't be
moving far enough in the bore to refill.

[K1300S]

You still have air in the system.  Follow Martin's instructions.  It takes a long time and a lot of pumping.

Is you have abs, make sure you do that first.

[Folsoml]

I usually prime the system at every connection starting with the master cylinder itself.  Fill it with fluid and hold your finger over the hole where the banjo bolt attaches.  Pump it until you feel air pressure build up on your finger.  Keep releasing the pressure until you feel good, firm, fluid pressure, then attach the fire brake line.  Repeat the process at the other end of the brake line.  Keep doing this with every component until you get to the caliper. 

[fsmechanic]

A vacuum pump from your local auto parts store is a great tool for bleeding brake lines.  Saves massive time.

[alexis291]

I had a similar problem on my 1995 k1100rs just recently when I had to replace the rear flexible hose. Obviously there was lots of air in the system after this. I have read lots of posts about bleeding brakes in different ways but this worked for me. The bike has ABS but despite what the Clymer manual says (take it to a dealer) this was not a problem.
I used a vacuum pump to draw fluid first at the ABS unit and then from the calliper. Air is drawn into the threads of the bleed nipple so I don't believe this is the best way to see all the air has been removed from the system but I pulled several reservoirs-full through to be sure. The trick I learned though was to pull the piston partly out of the master cylinder with it still in situ in order to get some fluid in there. Without doing this I had an airlock that just wouldn't clear. I pulled the piston back far enough so the first seal (ie the one that actually generates the pressure) passed the inlet from the reservoir.  This then allowed fluid to enter the cylinder so I could then push the piston back in and do up the retaining screw. It needed a bit of fiddling with the pedal height adjuster to get the actuation rod back into place on the end of the piston. Then bleed as normal.

[k100kiwi]

thank you for your comments and ideas.i reverse bled the whole system through the rear bleeder nipple then placed the caliper on the ground,put a small block of wood between the discs.then bled it,it worked perfectly and i had brakes within a few bleeds.