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Front brake lock up 1981 gl

Posted: Sun May 20, 2012 6:31 pm
by GL1100Newbie
I have a project 1981 gl 1100 with 34,000 miles. Got it running and after 80 miles the front brakes locked up after pulling away from a stop light. That was a real "come to Jesus moment". The front brake lever was non movable and the brakes would not release. I had to bleed the front brake fluid out to get the brakes to release and get the bike home.

The brakes both front and rear are two of the few things that I did not do anything with. Usually it is the things that I work on that stop working, so this came as a real surprise.

Has anyone had a similar problem? What is the fix? Is this just a front master brake cylinder rebuild? Or is just the front subordinate brake cylinders rebuild? Or both front master and subordinate brake cylinders rebuild?

Appreciate any help you can give.

Re: Front brake lock up 1981 gl

Posted: Sun May 20, 2012 6:40 pm
by virgilmobile
Read this post.The tiny pressure return port is plugged.viewtopic.php?f=11&t=46

Re: Front brake lock up 1981 gl

Posted: Mon May 21, 2012 12:06 am
by patbrandon1
More than likely Virgil is right. I did have an exception to this rule however. Indeed, make sure that little hole is cleaned out. A little tedious, but you can do it. My one time situation called for the right front caliper to be rebuilt. Did you feel the rotors on the bike when they locked up to see which one was hot?

But after you clean the tiny hole out, I would pull the lines, blow them all clean with brake fluid, and be very careful not to get ANY dirt at all in the lines or master cylinder. If the hole is plugged, the dirt or whatever caused it to get blocked, came from somewhere, and there could be more in there. On these bikes, never push the fluid back into the master when changing brake pads or the like. REMOVE the fluid and use fresh clean high quality fluid. That hole is very picky.

Re: Front brake lock up 1981 gl

Posted: Mon May 21, 2012 6:40 am
by virgilmobile
So far on my wings,i've had this problem on 4 master cylinders.Each one was not a foreign object,it was a result of moisture settling in the recess and oxidizing the hole shut.

Re: Front brake lock up 1981 gl

Posted: Mon May 21, 2012 11:32 am
by patbrandon1
virgilmobile wrote:So far on my wings,i've had this problem on 4 master cylinders.Each one was not a foreign object,it was a result of moisture settling in the recess and oxidizing the hole shut.
Good info Virgil. How does the moisture get in? And what can we do to prevent this? The time I cleaned mine out that allowed fluid to return again, I saw on the end of the wire I cleaned it with, little black specks. I actually thought maybe the brake line was deteriorating. Could the oxidation have black color to it? Thanks for your time on here, and being willing to share your knowledge freely.

Re: Front brake lock up 1981 gl

Posted: Mon May 21, 2012 1:13 pm
by virgilmobile
Aluminum will oxidize.You've seen it under the seal in the caliper.
Moisture comes from the air.Down here it's often 89 % humidity.
The brake system,even tho it's sealed ,is not impermeable to molecules of H2O.
Over a period of time,enough will collect and start to oxidize the aluminum.It can be black in color and turn whitish when dried.
There is no preventing this.
The best solution is as the manufacture recommends. FLUSH and replace all brake fluid at least every other year.
I do mine every year,because our high humidity.
People in the high desert can get away with a much longer time interval.