Front Brake Stuck

[cb1ocker]

Hello, I'm new to the forum, so please excuse me if this is the wrong place to post this issue, it started as an electrical issue, which is why I'm posting here.

I have a 1977 GS550 that I have been putting some work in to and mostly runs OK. That is until I replaced the turn signal relay yesterday. After testing it appeared everything was working OK, but I noticed that the front brake wasn't triggering the brake light. To be honest, I don't know for sure that this worked OK before replacing the turn signal relay.

To try to trace where the issue might be I started following the lines from the brake lever to try to figure out where the electrical for it was and where the issue might be. Long story longer, I couldn't figure it out, but while I was poking around and then testing the brake lever again the brake lever started feeling very stiff, could hardly press it in at all. At the time I stupidly didn't think much of it and decided to take it for a short ride to make sure everything else was still working OK.

About 5 minutes in I noticed a decrease in acceleration and I turned around, by the time I got back in my drive way the front brake was stuck on and I could barely push the thing back in to my garage.

I'm new to bikes and more familiar with electronics and computers than I am with the mechanics necessary to fix this, so here I am, looking for some advice.

Anyone know what I might look at to try to diagnose/fix this? Thanks in advance for any help you can provide.

[Eli69]

a lot of things could cause brake calipers or master cylinders to stick. mostly corrosion related. but one thing that you may not suspect is that sometimes the brake line hose gets plugged up inside. this causes the brake fluid to not return to the master cylinder and keeps the caliper pressured up.

loosen the bleeder on the caliper and see if the pressure is released.

on the electrical problem... did you check the switch on the brake lever?

[OldVet66]

The brake switch is under the lever. It can be cleaned, replaced or done away with and a more reliable pressure switch put on the master cylinder. Your tiny return hole in the master cylinder is clogged and heat from driving will cause pressure that will lock the brake. A master cylinder rebuild is in order. While you are at it you might consider replacing the brake lines with stainless steel breaded lines that don't expand as much and gives better stopping power. When you go to refill the lines you might find a vacuum pump real helpful.

[steve murdoch]

Welcome to the site.

Here is an excellent tutorial on a caliper rebuild. http://members.dslextreme.com/users/...e_overhaul.pdf

[Nessism]

Check the Newbie Mistakes thread linked in my signature. You need to do a full brake system tear down and clean out all the grunge, then replace the brake line and put the system back together.

[cb1ocker]

This is great, thank you all for the replies. I looked through the tutorial posted and I'll read through the Newbies Mistake thread and attempt the teardown and rebuild I think. Seems like for every 1 thing on this bike I fix 2 more pop up, but at this rate, I'll have the whole thing rebuilt in no time flat.

[cb1ocker]

a lot of things could cause brake calipers or master cylinders to stick. mostly corrosion related. but one thing that you may not suspect is that sometimes the brake line hose gets plugged up inside. this causes the brake fluid to not return to the master cylinder and keeps the caliper pressured up.

loosen the bleeder on the caliper and see if the pressure is released.

on the electrical problem... did you check the switch on the brake lever?

I have not checked the switch to see if that fixes the electrical issue, in fact I didn't even know there was one, let alone where it was. I'll do some searching around the forum and attempt to locate/replace it.

[Cyrano]

For the front brake electrical issue, (if it's similar to my 850) the switch harness goes into the headlight. They will be joined with male and female connectors. Disconnect the wires and try joining the bridging the two wires from the main harness. If your brake is now 'on' (remember to turn on the ignition) then the fault is on your brake switch.
This is a fiddly little fitting that has a brass bridge that slides over 2 brass contacts and makes the circuit. These are easily worn or dirty. I cleaned and made good my one but it didn't last and replaced it for a new unit.

As for your sticky brake, it sounds like a blocked return valve hole in the master cylinder. A fellow member had the same problem (with a rear brake) that was well documented here

Seems this is becoming quite a common problem. More here.

[cb1ocker]

For the front brake electrical issue, (if it's similar to my 850) the switch harness goes into the headlight. They will be joined with male and female connectors. Disconnect the wires and try joining the bridging the two wires from the main harness. If your brake is now 'on' (remember to turn on the ignition) then the fault is on your brake switch.
This is a fiddly little fitting that has a brass bridge that slides over 2 brass contacts and makes the circuit. These are easily worn or dirty. I cleaned and made good my one but it didn't last and replaced it for a new unit.

As for your sticky brake, it sounds like a blocked return valve hole in the master cylinder. A fellow member had the same problem (with a rear brake) that was well documented here

Seems this is becoming quite a common problem. More here.

Thanks for that, I read through those threads and that definitely sounds like what I've got going on. I read through the tutorials on BikeCliff's website regarding brake teardown and rebuild. For the electrical, I did notice that some wiring went from the brake lever into the headlight, this might be what you're referring to. I'm assuming you have to disassemble the headlight to get at those wires?

[cb1ocker]

finally got home from work and was able to troubleshoot some more. loosening the bleeder on the caliper released the pressure and the brake light also comes on when the lever can move more. the brake switch could probably still use a replacement but i think i'll focus on getting the brakes working properly first. on a positive note, at least my turn signal fix didn't cause the break light issue.

[BigD_83]

finally got home from work and was able to troubleshoot some more. loosening the bleeder on the caliper released the pressure and the brake light also comes on when the lever can move more. the brake switch could probably still use a replacement but i think i'll focus on getting the brakes working properly first. on a positive note, at least my turn signal fix didn't cause the break light issue.

losing your sense of humour isn't one of your problems...you'll do well.

[cb1ocker]

With how much money I've already sunk in to this thinking a shop could get me sorted out easier than I could do it myself I have to laugh to keep from crying.

As far as replacing the brake lines, I've looked in the GS Member Links section and there are a lot of different options for parts, do any of you have a specific resource you would recommend to order the new lines and any other parts I might need for this front brake job?

[BigD_83]

Raymond from Rennsport out of Missasauga, Ontario has been dealing brake lines for members. He might not have the best selection of covers in his lines, but I've worked with him a couple of times in the past, and I'm happy enough with the product he's provided. There may be less expensive, state-side options for you, although I suspect the strength of the US dollar would probably work out in your favour.

...and don't be getting ideas of a shop sorting you out at less cost. Your gained knowledge is invaluable, and too many shops don't do a good enough job.

[cb1ocker]

Is this the right site?

http://www.rennsportautoparts.com/

[cb1ocker]

Time for what are probably some really stupid questions, but I can't seem to find the answers and looking through the entire service manual I can't find the answers either, so I apologize in advance for my complete newbness.

It looks like the brake line goes to some kind of square connection mounted to the front fork, then another line goes from that to the front caliper. What is this called and does it need to be replaced during the teardown?

Brake lines are available in so many different lengths. If I just match generally the length of what is already in place will I end up OK?

Are the rear brakes part of the same system controlled by the same master cylinder as the front brakes or are does the rear have a different system?

Also, I guess this thread really should be in the Tires/Suspension/Brakes forum instead.