Today's Topics Rear Master Cylinder

[Maddevill]

Continuing working on the GS. Dug through my moldy dust covered boxes and dragged out the rear master cylinder from the dead flies
and mouse poop. I previously bought an overhaul kit so I'm good there. Took the snap ring and push rod off and.......nothing.
Piston just sat there, corroded into place. I sprayed it down with lubricant and tapped the plunger. It moved down in the bore...
and stayed there. Oofah. I tried air into the brake hose port and still no movement. Right now its out in the garage clamped in
the vice soaking.
The point of all this babbling is this I may be looking for a replacement master cylinder. Bike is a 1983 GS750E
If anyone has one or ideas on how to save this one, I await with baited breath.

Mad

 

[Nessism]

Assuming you figure out how to get the piston out be sure to use a flashlight down the bore and look for pitting in the aluminum. Brake fluid absorbs water and then the water causes corrosion. Of course, if people would change their brake fluid on the maintenance schedule this wouldn't be a problem but...

 

[mustangflyr]

Had a brass sleeve installed in front m/c of my '80 original bore diameter and no further corrosion issues.

 

[salty_monk]

I installed a MC off a Ninja 300 on mine. There is a post here somewhere. It wasn't difficult but did need a hole drilled in the bracket, the GS hole centers are different to most other more modern stuff.

Seems like one from a V-strom might also work. It works fine with the stock caliper.

 

[Maddevill]

ATTENTION Big Block is the winner. I continued soaking it and applied heat with a small butane torch. Still nothing.
So I got my roller stool over to the vice and while sipping a Modelo Negra and listening to my favorite light, family
style rock, ( Marilyn Manson), sat and tapped the body with a small brass hammer. After about 5 minutes... THAR SHE
BLOWS! Piston popped out. After cleaning everything the bore looked excellent so I rebuilt it. Another job done.
Big Block, your brand new Waffle Iron is on its way as a prize.
Thanks for all the help guys.

Mad

 

[grcamna2]

I have the same master cylinder on my 83' GS750ES and I have an OEM rebuild kit from Suzuki.My rear master cyl bore is too corroded and I want to replace it.I looked-up the part and they only give the part# for the entire rear master cylinder assembly:there's no separate part # for the body alone.Do you know if another model(550ES,1150?)will use the same rear master cylinder body where I can swap(14mm)the part in with no fitment issues ? thanks,Bill