rear brake woes...

[diegos_den87]

Hey everybody. last night I decided to change the brake fluid for my rear brakes as the fluid in the reservoir was a dark rusty color and I know the fluid has not been changed in at least 13 years. I should add that before I messed with them, the rear brakes worked fine. So I proceeded to drain the old nasty fluid and refilled the system with some fresh DOT 3, bled the system and all, and now the rear brakes will only grab if I pump the pedal several times, then they maintain a pretty strong grip after the pedal is released. I can release their grip by turning the rear tire, and after 2 or 3 good spins, the tire spins freely. then the pedal must once again be pumped several times to activate the brake. Also, I am getting little to no pressure at the pedal. any suggestions would be greatly appreciated.

-JT
Indiana
'79 GS750L

[jbs80106]

not sure...

but sounds like air in the line requiring pumping of the brakes, but could also be stuck calipers that need 'nudging' to engage and are then slow to release?

[diegos_den87]

so...

what would you recommend I do first? I don't think it is air in the line, I've bled almost an entire bottle of brake fluid through already.maybe a caliper rebuild could be the way to go? maybe while flushing all the nasty fluid through the system the bleeder valve became a dam, holding all the large chunks of crap back, gumming up my calipers? but would this explain the lack of pressure at the pedal? could it be in my master cylinder assembly? I don't know much about anything that's not explained in my Clymer manual so any advice would be great. Thanks in advance, -JT

[twr1776]

I would just go ahead and rebuild them with new seals, lines, etc. as needed. The OEM caliper kits do not cost very much. Not to be critical but a half a$$ fix could be very costly if they go out completely or stick on you at a bad time. Once you open up your calipers you will be glad you did. Here is a pic of the inside of a caliper of a bike that has never been left outside. I was just going to "run them" with new pads but I am glad I did not.

[diegos_den87]

thanks...

that's not too pretty, I imagine mine are probably worse, having sat for 13 years. and god knows how diligent the PO was about routine maintenance. Anyone know a good source for the complete caliper rebuild kit? How about a MC rebuild kit? might as well do that while I'm tearing my baby apart, once again.

[doctorgonzo]

that's not too pretty, I imagine mine are probably worse, having sat for 13 years. and god knows how diligent the PO was about routine maintenance. Anyone know a good source for the complete caliper rebuild kit? How about a MC rebuild kit? might as well do that while I'm tearing my baby apart, once again.

All the usual suspect parts sites (Bike Bandit, etc...) have them.

[twr1776]

Part # 1 appears to be the cup, seal, and dust boots. Part # 5 is also a good one to get while you have them apart. Check for BassCliffs website, I think he has a tutorial on rebuilding calipers in there. What part of Northern Indiana are you in?

http://www.partshark.com/fiche_section_detail.asp?section=94760&category=Motorcycles&make=Suzuki&year=1979&fveh=2134

[diegos_den87]

success!

Thank you everybody for all your help. This community has once again proven to be an invaluable resource. probably shoulda thought of flushing some cleaner through the system on my own, but I didn't. the brake works fine now. good pressure, engages and disengages as it should, all good. I'll probably take apart and clean up the caliper anyway, I'm sure it's ugly in there. What a relief. Ya, I used a smiley, what of it? Oh, and twr, LaPorte county, and yourself? I'll post some pictures soon so you all can enjoy the sight of my baby as much as I do(okay, maybe half as much.). I feel like the people here in this forum are at least 50% responsible for her return to life.

[diegos_den87]

my bike...

here's a pic for everyone to enjoy, I'd like to know what everybody thinks. keep in mind this is my first bike, 79 GS750L bone stock (when I got it).

[diegos_den87]

side view

view from the side

[diegos_den87]

from the seat

view from the cockpit, showcasing the 1 performance improvement I've made on the bike, a Nissin radial master cylinder. I know it's probably not necessary, but I prefer upgrading to simply replacing when a part craps out, as the old master cylinder did.

[diegos_den87]

oh yeah...

and here's my very first muffler burn from my first and only test drive, I hope it leaves a good scar, I kinda like it. I'm not nearly as fond of the two tickets that I got during the same ride. Who'da thought you NEED a license and a plate to drive a motorcycle around the block?

[Texas Don]

what would you recommend I do first? I don't think it is air in the line, I've bled almost an entire bottle of brake fluid through already.maybe a caliper rebuild could be the way to go? maybe while flushing all the nasty fluid through the system the bleeder valve became a dam, holding all the large chunks of crap back, gumming up my calipers? but would this explain the lack of pressure at the pedal? could it be in my master cylinder assembly? I don't know much about anything that's not explained in my Clymer manual so any advice would be great. Thanks in advance, -JT

If the brakes have to be pumped, then you still have air in the lines. First, the problem with your caliper grabbing is most likely that the piston is corroded or has foreign matter adhering to it that is causing it not to retract when pressure is released. A caliper rebuild is in order. There is an excellent pictoral to help you do this procedure. It is posted on bikecliff's web site at members.dslextreme.com/users/bikecliff/. When that is done, save yourself a lot of grief by installing speed bleeder valves instead of the standard bleeder valves. Your life will be a whole lot easier and you can purchase them directly from speedbleeder.com and you will need the number SB7100. When you are ready to bleed the rear caliper, do it by tying the caliper up higher than the rear master cylinder before you reattach it to the rear rotor. By having it higher, you are assuring that any air will rise up to the bleeder valve and be purged. Do not let the rear master cylinder reservoir run low or out of fluid while you are bleeding the lines or you will get to do it all over again. Once it is bled, tighten the bleeder valve or speed bleeder if you decide to go that way, and then reinstall the caliper onto the rotor and test it. You should not have to pump the pedal, and the caliper should release the rotor when you release pressure on the pedal.
Don