Front Brake Frustrations.

[Burk Ferden]

Hello Everybody,

I don't get it, I just don't get it. I have been working on rebuilding a 1980 GS850G and everything is working except the front brakes. I rebuilt the calipers and replaced the lines with steel braided ones from Z1 and I just can not get them to prime. I even replaced the master cylinder with a known working one, but I don't get pressure to build. I really don't know where to go from here to try to get the system to work. I would really like to get it working on my own instead of taking it some where since everything else including rebuilding the engine I did on my own.

The problem it not the master cylinder at this point because I took a working one off another bike to test it and nothing. When I put it back on the other bike it primes just fine. It must be something else. Does anyone have any ideas on what could be going wrong or if anyone has experienced anything like this before.

Thanks
Burk

[Nessism]

I’ve experienced this problem before with other GS bikes. My advice is to open one of the bleed nipples on the calipers and attach a clear hose to each which you can draw a vacuum on. The idea is to get as much of the air out as possible this way by drawing the fluid down from the master. After you get the majority of the air out this way, go to the other side. The master should start pumping now. To get the rest of the air out you need to work the brake lever quickly and kind of force those bubbles out with lots of fluid movement. Big waste of fluid but its cheap enough so don’t be stingy.

Hope this helps and good luck.

Edit: one other thing you need to do is make sure the sliding pins in your caliper are well greased. Just a kindly reminder in case you forget this step.

[lurch12_2000]

While helping a friend bleed the front brake on his Goldwing we just couldn't get it to pump up using the bleeders on the caliper. When we finally loosened (just barely until fluid oozed out)the brake line banjo connector at the master cylinder on the handlebar and slowly pumped the brake lever one time an air bubble released out the reservoir and instant pressure built up on the lever. Be sure you have a rag underneath so if it drips it won't get on painted surfaces.
Now I've bled my share of brakes and never had this difficulty, but it proved that a small air bubble can spoil your day.
A mighty vac might help.

[rustybronco]

Another ALMOST sure fire trick, take the brake lever off and use a wooden stick or dowel to push the piston. the piston will travel farther than with the lever.
try it...

[igotspam2]

I too have had this problem. What I found works best for front and back brakes is to get yourself a bleeder, but before your run out and buy the first one you know of, (like I did) and have it not work (like mine didnt) get yourself one that is realy just a large serenge that you fill with fluid, and it has a small hose on the end. You take off your cap then loosen the bleeder valve, put the hose on the nipple and fill your breaks from the calliper up. be careful not to push in any air. This worked instantly for me , I got pressure so i could go ahead and work out the rest of the tiny foam like bubbles. My buddy has built bigdogs for the last 8 years and said this is how they fill their brand new bone dry breaks. Hes witnessed guys pumping and pumping with no results and this technique helped them and me from pulling out any more hair!! Hope this helps. Also, im not sure if this is the same for the front cause ive never been inside the master on my front breaks but, When I got my bike I had to take apart my rear cylinder and free up the piston inside, it isnt attached to anything inside and was just wedged up and stuck.