GL1000 Rear Brake issue

[cfairweather]

I am doing two projects at the same time. Today, I installed the rebuilt rear brakes (master cylinder and calipers) on both bikes. One went fine, but the other didn't go so well. I think there is something wrong with the master cylinder and will figure it out tomorrow, but I thought I would see if anyone has see the problem below:

Here is what I did, so you have the whole story:

To test the brakes, I installed a blank hub, with just the disk on it. On the first bike, I would turn the hub and then pressed the brake to make sure it would stop the rotation. That worked and when I released the brake, I was able to easily turn the hub. Now to the second bike...I removed the hub from the first bike and installed it on the second bike. When I press on the brake, it stops the rotation; however, when I release the brake, I notice that the hub does not easily turn. If I press on the brake again, it stops the rotation but when I release it, the hub is even harder to turn. So, I thought to myself, it seems like the pressure is not fully releasing when the brake is released. So to test my theory, I simply opened the bleeder for a second and then closed it. Sure enough, the hub was easy to turn again, so this tells me the master cylinder is not releasing the pressure. Again, each time I press on the brake and release it, the hub gets harder to turn. The pressure seems to build up, but doesn't fully release when the pedal is released. I did check to make sure the small hole in the master was open but I will verify this again tomorrow.

[Whiskerfish]

yea check the spooge hole and if you put a rebuild kit in the M/C check the spring length compared to the original. Liam's 1200 had us chasing our butts for hours with a bad aftermarket rebuild kit.

[ritalz]

That sure sounds like that tiny hole is still blocked. I use a single wire from a large wire brush and watch for it to go through into the bore. It don't take much to cause a blockage. Also, if you removed the plunger during your work be sure you assembled the plunger parts correctly. Easy to miss a small detail.

[robin1731]

Could also be the brake hose. They can break down over time and let fluid move one way but not the other. Much like the return hole in the master cylinder. You can test that by loosening the brake line at the master cylinder and see if the pressure releases.

[redglbx]

Cedric, as the others have said it’s probably the spooge in the m/c , just use a very small wire to carefully clean it. That’s probably it but as also said it can be the hose as well, when I was working at the Brake supplier Chrysler had a big recall (as did others) where the brake hoses were delaminating and causing a flap internally that acted as a check valve & held pressure.

So clean the spooge and if that doesn’t clean things up then replace the hose. I highly recommend a set of braided stainless lines, they really improve the braking & feel.

[cfairweather]

Thanks to all for the great advice. I cleaned the tiny hole and it solved the issue. I used a #80 drill bit to poke it into the hole and then used a slightly larger carb cleaning wire to finish the job. A number #80 drill bit is the same size as the #35 slow jet hole in a GL1000.