• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

GS1100 Front Master Cylinder Rebuild Woes

  • Thread starter Thread starter AOD
  • Start date Start date
A

AOD

Guest
Long story short, I'm upgrading my front braking system to stainless steel lines, soft Ferodo pads, and I figured I would rebuild the master cylinder - since it couldn't be perfect after 22 years of use.

Initially I found there to be no rebuild kits listed for '83 GS1100E bikes...kind of odd. Then a few came up on ebay:

http://cgi.ebay.com/ebaymotors/ws/e...RK:MEWN:IT&viewitem=&item=150099779008&rd=1,1

http://cgi.ebay.com/ebaymotors/ws/e...RK:MEWA:IT&viewitem=&item=180102340739&rd=1,1

I bought one, not knowing what the internals of mine looked like. After finally getting mine apart, here's what I find:

mc-rebuild-4-6-07-003.jpg


The bore was full of rust and crap, so I'm glad I took it apart. However, it looked completely different than my rebuild kit!!

mc-rebuild-4-6-07-005.jpg


Okay...so I bought the wrong kit. They must be right...no rebuild kit available. I look up the Suzuki microfische at Alphasports, order the part number from the '83 GS1100E and it comes in the mail:

mc-rebuild-4-6-07-007.jpg


WTH!?

It's an 8-mm sized bore and my bore is at least 10-12mm - IT WONT EVEN FIT. Needless to say I haven't opened the package, but I'm not even sure how I'm going to return it.

Disgruntled, I put the master cylinder back together with the original parts...hook up a brake line and master cylinder, pump away and it throws fluid down the line, but won't push out the cylinder. Apparently it's trashed.

The ebay kit has the correct size, but I can't fit the snap-ring washer over the piston:

mc-rebuild-4-6-07-006.jpg


I may go to a hardware store and see if I can find one that is the same OD and bigger ID...but I'm on a prayer at this point.

Thoughts and feedback are welcomed. I needed to rant.

~Adam
 
Somebody with an 83' , or more knowlege better chime in, but mine looks just like your original one. I have no idea what that spiral on your replacements is about. Doesn't look at all the same. I bought a new Suzuki piston assembly for mine. It looked exactly the same. My MC is marked 5/8 's.

Actually, I just looked, and where I bought mine, it lists the same MC for the 82-83 http://www.flatoutmotorcycles.com/fiche_section_detail.asp (sorry, the link won't go directly to the page I want) It's Part # 59600-49830

BTW- I order a lot of NOS Suzuki parts at Flatout, off the fiche. I don't buy aftermarket parts very often.

Here is mine disassembled. It's from my 82 GS1100E
IMG_1146.jpg
 
Last edited:
If you are not worried about a concours bike then go down to the wreckers yard and get a master cylinder off a Kawasaki ZX9 or 10 (mid 90's model). It has a 5/8 bore and will improve your front brake immensely and looks good. Also has an adjustable lever on it too and a more modern, easier to work on, brake light switch.
 
Deny,

I'll look up the part number for the 82 GS1100E and see how it compares to my '83. My master cylinder is 5/8, so if I can get what you received in your kit...I might be able to salvage mine!

~Adam
 
I did a sanity check on my behalf and I see I was sent the wrong Suzuki part number for the master cylinder. Not sure how the mixup occured, the order to the website had it correctly.

~Adam
 
Ya, I thought I saw in your last picture what looked like the wrong part#.

BTW- For future reference, Flatoutmotorcycles sells that part for $12 less than Alphasports, and I think the shipping charge is about the same. I seem to always find the lowest prices there.
 
I called my local dealer where I ordered the part today. Their online order system lets you put the Suzuki part number in and it's price was $10 or so cheaper than BikeBandit, and it arrived in 4-days.

I had them order the correct part number this time and I'll do an exchange. Hopefully I can salvage my master cylinder still! :)

~Adam
 
Call this FYI for those that have an 1100...don't order a rebuild kit off ebay!!
 
You are correct in that there is no aftermarket front master cyclinder rebuild kit made for your bike. many vendors carry rebuild kits, but they are all mfr'd by K&L, and K&L does not support every model. it is hit-or-miss. Whatever you got from the Suzuki dlr is obviously the wrong part. Perhaps it is for a rear brake? it would seem that some dweeb messed up, so go back and demand a refund or exchange for correct part(s)
 
Got the correct master cylinder kit from Suzuki today, it looks right. I'm putting it together now, but I just wanted to note that it did not come with the o-ring that fits on the block piece that slides on the piston shaft. FYI for those considering a rebuild.

~Adam
 
Grumble.

The master cylinder is rebuilt with the correct kit. It's pushing fluid out and down the lines, but I can't get it to build pressure. I've released the banjo bolts, pumped the brake and bled the bleeder screws. The lever still pumps away with no effort.

No leaks or whatnot I can see. :(

~Adam
 
Try this. Remove the brake lever from the M/C. Remove the lid to the fluid bowl. Push the piston all the way in with the old piston or a phillip screwdriver. Watch in delight as air bubbles rise to the surface.
I went through an entire day cursing the bleeding process. The brake lever does not push the piston all the way in so it leaves room for an air pocket.
 
Chef,

I search the forum earlier and found a previous post where you suggested this and it worked. I thought to myself, awesome, I'll go home and do this!

Welp, no luck. I used the old master cylinder piston and pushed it in as far as I could many times. No pressure. I then bled the master cylinder again, no luck. I bled the calipers again, no luck.

There's two things I can think of now that might be the problem:

1. I used a c-clamp to push the brake pistons into the caliper when I put new pads on. Could they get stuck there in some weird fashion and not 'push back out'?

I bought a might-vac just now and I'm going to try power bleeding them to see if it helps.

2. I installed the primary cup backwards on the piston shaft during my rebuild (and/or something else when bad in the master cylinder)

mc.jpg


I put the primary cup inward to where it fit inside the one end of the secondary cup. If you look at the picture above, the arrow points to the cup. I put the side that is facing upward in the picture facing outward of the large diamter side of the piston.

I will try to show it with symbols:

[---[]-<|--

Can someone confirm which way that cup needs to go?

~Adam
 
Last edited:
I was confused by that part as well. But I'm pretty sure now that the grooved face (the side facing up) of #7 facing into part #6.
 
Looks like my internet is working again at home...good thing I stayed up late to bottle some of my home brew and try a batch that finished carbonating. ;) Unfortunately the only good news tonight is that my beer turned out good....my brakes still don't work.

A HUGE thanks to Deny and Chef...I PM'ed these guys my cell phone because the net was down and they both called me 20 minutes apart. This forum is great. :)

Deny thought I should reverse the way my secondary cup was installed, so I went ahead and did that. Mounted it back up, pump pump pump...pushing fluid but still couldn't build up pressure.

I then removed the front calipers, hooked them up to the rear brake line and pushed the pistons out. They both moved.

Put the calipers back on the front, bleed them, but the master cylinder still won't build pressure.

I'm at a total loss now. I'm going to be making ebay offers for a used master cylinder. :(

~Adam
 
AOD said:
Put the calipers back on the front, bleed them, but the master cylinder still won't build pressure.

I'm at a total loss now. I'm going to be making ebay offers for a used master cylinder. :(
Click to expand...
I know it's frustrating, but I wouldn't give up. Many of us have been in your exact situation. How are you going to feel when you get a new/used master cylinder, and it won't build pressure either? :)

I've been through this not too long ago. Pumped on that limp lever for two hours! I think you've seen all the tips, and have read this thread. http://www.thegsresources.com/_forum/showthread.php?t=98788&page=2&highlight=bench+bleed

I followed the advice of rustybronco in post #12 with good results one time. It's kind of like bench bleeding a master cyclinder, but that sounded too messy. I could feel the fluid pressure on my finger as I held it over the hole. Then I just had to re-attatch and bleed the line(s).

If you keep at it, I bet you'll eventually get it working.

BTW- I think even if you had that seal reversed, the master cylinder would still work, but maybe tend to leak just a slight amount.
 
The U shape opening faces the direction it will travel when engaged. If the seal is backward it will not build pressure. Make sure both holes in bottom of reservoir are open or it wont work. If you had crap in the mc you will have crap in the holes and if it can't pull fluid when retracting it can't expell the air. If it's working correct the fluid will run out of the bleeder with no lever action and you keep putting clean fluid in till it runs out clear. Another trick is to compress the brakes with a c clamp or big pliers before bleeding and don't let the reservoir run dry when bleeding.
 
:?

After rebuilding the front master cylinder for my 1980 gs550, I also found it to be impossible to get pressure in the lines. I found a great trick by accident: I had a hand pumped syphon thingy and I hooked the "suck" end to the bleeder valve. Next I pumped it until there was a mild vacuum in the pump, then I opened the bleed valve and closed it again after about 2 seconds. I repeated this a few more times and when I got back on the brake lever... WOW! Like magic, I finally had brake pressure! I figure by sucking the fluid thru the lines instead of just pushing it the bubbles get sucked right out. Good luck!
Click to expand...

I will try try try try try again to bleed the master cylinder. I did the above method many times...in fact I've now put an entire small bottle of brake fluid through the front!

I used my mighty-vac to create 5 PSI of vaccum then I crack the bleeder valves and watch it suck fluid through. I can get it to a point where there is no air coming out of the bleeders....but the brake lever is still soft! :mad:

I did notice that as a pump the lever I get a small 'fountain' from the master cylinder holes. I think the smaller one is pushing fluid up....and if I remember right, it did this last year when I bled the brakes, prior to my rebuild.

This is just damn frustrating.

~Adam
 
Hey guys, update here. I came home today and found fluid sitting on the ground under the master cylinder and wheel area. I tightened up the banjos and didn't see any leaks. Left again for a bit this evening, come back and more fluid under the master cylinder area.

There's a machined hole on the bottom of the master cylinder, near the brake switch area. It's wet...it makes a bubble / air noise when I pull the lever. What is this hole??? :? :?

~Adam
 
You must log in or register to reply here.
Back
Top