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Master Cylinder rebuild

  • Thread starter Thread starter rickt
  • Start date Start date
R

rickt

Guest
I managed to remove the front master cylinder and caliper from my recently-acquired '78 GS750 this afternoon. The small amount of remaining fluid was rust-colored and nasty. Not surprising for a bike that has been sitting for 25 years. Well, following instructions in the Clymers, I looked for a circlip that held in the piston. After I removed the rubber boot, I could not find anything that resembled a circlip and it would appear that removal of the piston is not possible. Have a missed something here? I really need to rebuild the MC to have any chance of salvaging the front brake.

Rick T
 
The circlip is down in the bore. Maybe you have some brown crud covering it over?

Finding the clip is easy compared to getting it out. You need some special plyers and a lot of patience. Good luck...you will need it! ;)
 
If your piston is not stuck in the depressed position, the circlip should be right on top of the piston outer circumference. It keeps the piston from coming out any farther from the piston spring pressure.

I know mine was very dark and crusty under the boot, and I destroyed the boot getting it out, it was stuck so bad.
 
I see it, but how to remove it?

I see it, but how to remove it?

Yes, after the boot was removed, I see what looks to be a circular clip. This does not resemble the circlips I have removed when rebuilding other cycle MC. There are no tabs with holes for circlip pliers. It looks just like a piece of wire in a groove. I'm not sure what kind of special tool would work on this type of clip.

Surely some readers have dealth with removing this tricky little clip before?

I'm open to all suggestions!

rickt
 
Brake reservoir

Brake reservoir

While I'm dealing with the front brake situation, possibly someone can give me a hint on removing the front brake MC reservoir. I guess I'm not surprised that 25 years would cause such things to sieze, but there must be a trick or two to loosen it up.

rickt
 
Hello rickt, I have messed with a couple of these rusty old master cylinders and after removing the one or two screws that secure it, its prety much a matter of brute force and a twisting motion. There is an o-ring that seals the resevour to the cylinder. I put the cap back on mine and used it to gain leverage when twisting but other then that I wouldnt use anything but your hands to twist the resevour off of the cylinder.
 
I'm doing my '79 850 right now, have been able to (finally) get the snap ring out but am unable to remove the piston. The rebuild kit includes a washer and am guessing that is what is corroded in the bore and keeping the piston from releasing. Sprayed liquid wrench in and am leaving it for several days in the hope it will then wiggle free. Want to be careful as new master cylinders are no longer available.
 
Try update to newer model

Try update to newer model

If this becomes unusable... try moving up in years a few until they have one in stock... make sure it is for a round bar or a square bar depending on what you have installed on your bike.. also if the it is a 7/8 inch bar.. you could possibly use one from a honda 750... say 79 supper sport ( twin front discs) or as cb 900 super sport. They all are close in looks and should fit.. the only rub is it would not be all Suzuki... but then again.. the r/r makes most not all Suz's either..

my $.03 (inflation hit me bad this year)

JP
 
It seems to me when I did my 750 there was a washer on top of the circlip. After cleaning and blowing it out and probing with a dental pick I finally got that out and could see the circlip. Then the real fun began. It takes circlip pliers with very long tips to get down in to get the clip out. Do yourself a favor and get the right tool for the job - http://www.mikesxs.com/mikesxs-tools.php?category_id=7.1 scroll about half way down to the Right Angled Snap ring Plier Set.
 
Success! Finally got the whole assembly apart and back together and it works! The snap ring is down there altho I had to buy a 7" snap ring plier set, internal and external to get it out and then back in. There is a washer below the snap ring to protect the plastic piston when you pull in the brake level. It was badly rusted and I left it in liquid wrench for several days. Gave it a gentle tap with a long punch and it popped right out. The piston bore was quite rusty but cleaned up with new brake fluid and cotton swabs. Just in time for it to start snowing.
icon13.gif
Ah well....
 
I slapped a Ninja MC on my GS750, and if I recall correctly I had a Yamaha MC on my Shadow. Upgrading the MC on my GS was a necessity (didn't have one when I got it), plus rebuild kits are easier to find, it was in great shape, modernized brake switch (you have to cut the old switch off and put small connectors on the wires, no big deal), and IMO it looks a lot better. As long as it fits the bars and has the same set up (single or dual disc) it should all bolt on.

I'm assuming that square bars are clip-ons? Unless you're running some funky 70's bars.......
 
would like to know where you all buy the rebuild kits for the MCs? I would like to do my front MC as well. The rear was just done by the mechanic and all he did was take it apart, clean it, and put it back together. I would like to change any moving parts I can out, plus put a new boot on. Also, the caliper. Other than a dealer, I can't find parts for these things? I've tried the links on this website, but they don't have complete stocks.

My bike:

1980 GS550E

Thanks
 
RickT, I'm new to GSR, so bear with me. I have an 83 GS850L that's been sitting for 10 years and I just began getting it going again. The sight level? in the side of the MC had deteriorated and when trying to scrape the dirt off, I punctured it. Short story, watch EBay. I found a like new replacement for $10 =S/H. While I was looking, I saw plenty of them for older bikes with 4 screws in the cover (mine only has 2). Of course, if you get one of these, there's no guarantee it won't need rebuilding also! Good luck.
 
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