Reviving on a 77 gs 750

[brandman]

Hello everyone. What an informative forum this is.
I have a 77 gs 750 that has been sitting indoors since 1985. The brakes(front and Back)had no fluid in them until a few days ago when I filled the the cylinders to make an attempt at bleeding them. With full cylinders no amount of pumping on the brake levers produces a response. Nothing is coming through the bleeder valves. I assume there is something else I need to do, I'm just not certain what.
Jack

[Suzuki mad]

Hi, what is the lever like to pump?

Did you release the 8mm bleed nipple on the calliper before pumping with fluid in the master cylinder?

It does take a while for fluid to go down the pipes.

One idea is it to remove the banjo bolt and pipe from the master cylinder and placing you thumb over the open hole pump the lever to see if you are getting any fluid to move or pressure on your thumb.

If you get pressure then quickly replace the pipe and bolt, then bleed the brakes as per normal?

If not then it would appear that the seal within the master cylinder has failed with age and lack of fluid. This will mean you have to replace the seal which is not too hard a job.

Suzuki Mad
1981 GS1000ET a little poorly
1983 GSX1100ESD fully restored. Boy, was it that quick all those years ago?

[brandman]

Reviving brakes on a 77 gs 750

Thanks for your reply Susuki Mad,
There is absolutely no preasure on the front brake lever to the point of the lever being floppy. I don't believe I loosened the bleeder valve when I first began pumping the lever. But have done it in this order since. I will follow your advice on checking the seal in the master cylinder. Thank you again.
Brandman

[SqDancerLynn1]

The 77 I have I had to replace on of the front brake lines Start by removing the brake hose from the master. holding your finger over the outlet try bleading the master, then check the lines & then try bleading the calaper

[brandman]

Riviving brakes on 1977 gs 750

Thank you for your reply SqDancerLynn1.
I removed the banjo bolt and tryed pumping the lever and still nothing.
I have since removed the master cylinder. I removed the snap ring in an effort to remove the piston and cup set but the set is frozen in the cylinder body. I'm letting it soak in brake fluid overnite. Looks like a Master Cylinder rebuild is in order thus far.
Brandman

[txironhead]

Honestly, if your bike has been sitting for 11 years, you're probably looking at a complete brake rebuild. Old contaminated fluid crystallizes in the lines and can clog everything up. My bike had been sitting for about 6 years and all of the brake parts were full of the crap. I rebuilt all three calipers (basically cleaned and reassembled them, the seals were fine), flushed the lines thoroughly, and ended up having to replace the master cylinders. The front MC was missing the reservoir completely and frozen solid, so I replaced it with a Ninja unit from a dual-front equipped bike (now I have an adjustable lever, too! Also eliminated the old-fashioned brake switch with a modern replaceable one.) I'm still trying to find another rear MC, as soaking it in Corrosion X for a week did nothing. If you can rebuild your MC's then great, but you need to completely clean the old crud out of every other component.

[brveagle]

Actually i think it's been sitting for 21 years.... Yikes that's a long time...

If i were you, i'd get on ebay and find someone parting out any gs brake assembly, the whole thing and just get that. Make your life easier...

[brandman]

1977 Break repair

Thanks for all your past responses folks. I'm still working on those brakes when time allows.
I'm tackleing it again after a few months.
I have replaced the piston and cup set in the front master cylinder. Fluid is moving throught the line now perhaps not enough because I still cannot seem to get any firmness in the lever. Perhaps the o ring seal in the cylinder reservoir?

[dardoonk]

I just pulled the brakes off my 77 GS750. (last registered in 82). After tearing apart the master cyl, I just threw it away. Fluid had gelled in the cup and the master cylinder had leaked empty, that left me with a rusted corroded piston. Lines were clogged and brakes frozen. If all this sounds familiar, rebuild or replace everything. Not stopping is a BIG problem.

You can make about any 7/8" master cylinder work. I bought a ZRX1200 mc off ebay for $39.00 and landed two calipers & disks from GS1100 for another $20.00. Now bingo! I've converted my single to dual disks.

[chef1366]

Take the hand lever off and the cap off the master cylinder. Bleed the master cylinder itself by pressing in on the piston with a screwdriver all the way in and hopefully you'll get some pesky air bubbles to come up. You'll never get the lever to firm up with the air in the master cylinder. Once you get the air bubbles out of the cylinder do a gravity bleed through the lines to the caliper bleeders. Don't let the master cylinder empty out. Then close the bleedeers and pump your brake lever and open a bleeder at at time and pull in the lever close the bleeder and release the lever. Repeat till all air is bled out.