Front brake bleed on '79 GS550L

[tbrand69]

Okay gentlemen, I've been trying for two hours to get this little a$$hole to bleed. Here's the stats:

Brand new SS lines and fittings from Earl. I took extra care when making them and installing the olives and making sure there were no kinks in the lines.

Rear line took me less than five minutes to get the fluid and air bubbles flowing. I used the pumping and hose sucking method described on this forum. The rest of the time was spent fine tuning the rear line and topping off the MC.

The front wasn't so easy. No matter what I've done so far, nothing has come out. I've sucked, pumped, lid on, lid off, repositioned the MC, hung the caliper so the line is above the bleeder, nothing. Not a damn thing.

Questions:

1) Should I be continually seeing air bubbles in the reservoir every single time I pump the lever?

2) Should I just let the bastard sit over night and try again in the morning?

3) Is a new tool (mighty vac, speed bleeder, etc.) necessary?

4) Should the MC be placed in any particular position? For example, where should the little holes at the bottom of the reservoir be sitting?

5) I disconnected the line from the caliper and nothing came out. What gives?

Any insight into this would be most appreciated gentlemen.

Tommy

 

[Bass Man]

tbrand69,

While getting my 81 back on the road this summer, there was all kinds of 'melted' rubber clogging everything from the MC to the calipers. I replaced the OEM brake lines, cleaned out the calipers, but also had to rebuild the MC since it was clogged up as well (nothing coming out, no air, no fluid). I assume your MC was working prior to the new lines? If yes, maybe crud got in while it was apart. Could be a candidate for a rebuild/replace?

Hope it helps...

 

[Nessism]

Sounds like the small bleeder hole in the master cylinder is clogged. This hole allows fluid into the master cylinder interior to prime the system. You can sometimes draw fluid into the pumping chamber using vacuum on one of the caliper piston nipples, but even that won't work if the master is clogged. I suggest you pull out the master cylinder piston and make sure everything is clear just to be safe.

BTW, great job doing the brake lines.

 

[Sadsak]

Sometimes when you've had it all apart and completely drained you have to "bench bleed" the master cylinder. This can be done on the bike but be very careful not to get any brake fluid on your painted parts.
Remove the fitting holding the hose to the master cylinder and place your finger gently over the hole. Squeeze the lever, release any pressure build up, then press your finger firmly over the hole and release the lever. This should push the air out of the master and draw fluid back into the cylinder from the resevoir. Repeat a couple of times and you'll be squirting brake fluid all over yourself.
If this doesn't result in pressure then the master cylinder has issues and will need a rebuild, or at the very least a good cleaning.
Good luck and let us know how you make out.

Sadsak

 

[tbrand69]

Thank you gentlemen, I shall take a closer look at the MC. I forgot to mention that I did rebuild the caliper and MC with all new parts. Looks I might be having to take the MC apart again. Anybody know what stores carry the motion pro circlip pliers tool

 

[tbrand69]

Sometimes when you've had it all apart and completely drained you have to "bench bleed" the master cylinder. This can be done on the bike but be very careful not to get any brake fluid on your painted parts.
Remove the fitting holding the hose to the master cylinder and place your finger gently over the hole. Squeeze the lever, release any pressure build up, then press your finger firmly over the hole and release the lever. This should push the air out of the master and draw fluid back into the cylinder from the resevoir. Repeat a couple of times and you'll be squirting brake fluid all over yourself.
If this doesn't result in pressure then the master cylinder has issues and will need a rebuild, or at the very least a good cleaning.
Good luck and let us know how you make out.

Sadsak

I attempted the bench bleed twice. Both times I was able to get fluid to continually pump out of the hole.

Please note that after the first bench bleed failed, I took the banjo and line off again and nothing was flowing at all.

I used a rubber band to hold the lever down while I reattached the banjo bolt while the fluid was still flowing. After reattaching everything I still have no brake pressure.

I can feel some pressure build up after five to ten pulls, and I can hear an audible "phoof!" when I open the bleeder valve. But absolutely nothing else comes out, no matter how many times I pump.

 

[tbrand69]

Here are some pics of what happens with my reservoir:

Here is how it is currently situated:

Here's what it looks like in its resting state on the inside:

And here's what it looks like after every single time I pump the lever:

Bubbles! Bubbles everywhere!

There has to be an air leak somewhere. The fluid flows when I bench bleed the MC, and the bubbles appear to stop as well. But the fluid stops flowing when I reattach the banjo and hose, and the bubbles come back.

There is zero signs of fluid leaking anywhere. Is the reservoir situated correctly? Does it matter what holes are covered or exposed?

 

[Nessism]

I want to say bubbles are good as that suggests air in the system is purging out the top. Keep working it.

 

[tbrand69]

Update

Update

I went out and bought a mityvac. Pretty cool tool. Unfortunately it did not do much. Well, it did something.

I took the MC apart and cleaned it out with brake cleaner. I double checked all of the piston assembly's parts were there and in order. I made sure all the rubber inside was intact and good to go (it should be since they are brand new parts).

I reassembled everything and bench bled the MC in a vice. If I did it right I could shoot a nice clean stream of fluid across the garage. After feeling the pressure build underneath my finger I depressed the lever and held it there while I hooked up the banjo and line.

As for the mityvac, I could build up about 21 inches of pressure with the bleeder closed; once i opened the bleeder I could hear a huge swell of air and see small amounts of fluid trickle down the hose. If I kept pumping I could get the pressure up to about 17-ish inches with the bleeder still open.

Unfortunately, I pulled about 60 mL of fluid out this way, and not once did I get a consistent stream of fluid to come out. It trickled the entire time, and only when I had built up pressure before opening the bleeder.

The brake doesn't even squeeze the pads together, not even a tiny bit. The lever goes all the way back to the bar with a slight spongy feel.

I'm nearing my wit's end here.

 

[subforry]

I have used a MityVac for years and almost never get a solid flow a fluid. There is usually air leaking at the bleeder or rubber connector or maybe the vacuum is boiling the fluid. The point is don't think you need a bubble-less flow to get the job done.

If you use the lever down, open, close, lever up bleeding method then yes there shouldn't be air in the bleed hose.

I went through some of this hell myself. Turned out the caliper pistons were sticky. My post might help you:
http://www.thegsresources.com/_forum/showthread.php?t=200027

Does a GS550L have 1 or 2 front calipers?

 

[tbrand69]

I have used a MityVac for years and almost never get a solid flow a fluid. There is usually air leaking at the bleeder or rubber connector or maybe the vacuum is boiling the fluid. The point is don't think you need a bubble-less flow to get the job done.

If you use the lever down, open, close, lever up bleeding method then yes there shouldn't be air in the bleed hose.

I went through some of this hell myself. Turned out the caliper pistons were sticky. My post might help you:
http://www.thegsresources.com/_forum/showthread.php?t=200027

Does a GS550L have 1 or 2 front calipers?

It has only one caliper.

 

[tbrand69]

I noticed that fluid was leaking from the MC near the banjo the other night after letting the bike sit for a couple days. It wasn't leaking before, but I guess I'm used to surprises at this point.

So I think I'm going to be as thorough as possible here and just order a new piston for the caliper, and new banjo bolts. I can probably grab the banjos from a local dealer, but I will order a stainless steel piston from Wemoto or some place. I don't want to take the chance of having the piston sticking as the problem, so I'll be diligent and take care of it.

 

[Nessism]

If you order new parts I strongly advise to only use Suzuki branded parts. I've experienced problems with aftermarket brake system parts. It's not worth it.

 

[koolaid_kid]

Except for the hoses. Use only stainless steel hoses, new banjo bolts and crush washers.

 

[tbrand69]

If you order new parts I strongly advise to only use Suzuki branded parts. I've experienced problems with aftermarket brake system parts. It's not worth it.

Except for the hoses. Use only stainless steel hoses, new banjo bolts and crush washers.

Alrighty then. I don't know how much a Suzuki piston is going to cost, but I'll look into it. And I will buy the banjos and washer from Suzuki as well.

 

[tbrand69]

New update

New update

So I got fed up and just switched out the new plunger assembly for the old one. I just wanted to see if it made a difference or not. Well, it might have, because the fluid started flowing, finally. I literally had to refill the reservoir 4 times. The mityvac just kept on pulling.

I will disassemble the MC and put the new (Suzuki) assembly back in and bench bleed again. I think the bench bleeding is what made the difference.

But get this: the lever still felt like mush. Just pure mush. No matter how much fluid I put back in or took out, I got nothin.

It has to be the caliper. Something is wrong with the piston maybe? I pulled the caliper off and literally felt no movement whatsoever in the piston. I will disassemble it and see if anything is sticking. This is just maddening.

 

[oldrookie]

Couple of ideas from a guy that has been fighting with a MC since spring. Try putting some teflon plumbers tape around the threads on the bleeder.

Put a thick coating of grease around the base of the bleeder and the MityVac line when you are getting ready to pull fluid.

Suspect your front seal in the Master cylinder. Fluid comes out the end and trickles down to collect on the banjo bolt and makes it appear that the banjo is leaking.

 

[tbrand69]

update

update

Okay gentlemen, I got everything taken apart and here are my findings:

the axle bolt o-rings are no bueno:

That's how they came out when I stripped the caliper. The original o-rings were hard and broken, so I threw some new ones on there. Unfortunately, I just used some spare o-rings I had laying around from the carb parts I ordered from our mutual friend on the GS forum. They fit well enough so I figured "screw it."

Well, I noticed the caliper holder was pretty stiff. It would barely move unless I really pushed on it. I'm pretty sure those o-rings are the reason why, because I remember that the bolt was a pain in the ass to get back on when I originally installed them.

I'm gonna order some new parts now and try again. However, no place sells original Suzuki pistons for my bike. No parts fiche carries them from what I have seen. Wemoto carries them, but they are not OEM. I may not have a choice here. The piston had some pitting:

Suggestions, gentlemen?

 

[tbrand69]

Update

Update

Been on vacation and dealing with some other things for the last month or so. Got back and had some new parts waiting for me:

Seal for the front piston, o-rings for the axle bolts, diaphragm, plate, reservoir, and hardware for the MC.

Installed everything, bench bled the MC (it shot clear across the garage), whipped out the MityVac, and didn't get sh!t.

Recap:

New o-rings because old ones were shot:

Bore is clear:

The order of the plunger assembly I installed:

Very little comes out of the caliper while bleeding. I've pulled maybe 30mL so far, and had to refill a couple times, but the lever is complete slop. There is no resistance until it is almost fully depressed, and even then it's a total sponge.

The reservoir is still filling with bubbles everytime the lever is pulled in.

I'm at my wit's end here. I literally have no idea what the hell is wrong with the damn thing. The bike is running now thanks to tkent's fuel tank, and I just need to tune it. But the bike isn't going anywhere until I have a working front brake.

Any help or advice you guys have would be really nice right about now.

Tommy

 

[john82q]

In your picture you have the spring the wrong way round...

the primay cup (rubber bit) goes toward the piston...