Rear brake master cylinder

[Pelkekal]

Hey everyone,

I am working on my project bike (1978 GS750) and am looking for a new rear brake master cylinder. The original is leaking fluid badly, and it already messed up the paint. I’m having a hard time finding a new replacement for it, but have seen the rear master cylinder for the GSXR’s to be in a huge abundance online. My question is, can I use the cylinder from a different Suzuki bike and it still bolt on/hook up and work well? Or will I have to use the GS750 one specifically.

[dorkburger]

You could probably get a rebuild kit depending on what condition the bore is in. It's a pretty simple device.

[Nessism]

Rebuilding the master is possible, as long as the aluminum bore isn't all pitted. Partzilla sells master kits. They are not cheap.


Adapting a different master is an option. This thread has some good info to that ends...

https://www.thegsresources.com/_forum/forum/technical-forums/performance-tuning-mods/84031-rear-master-cylinder-gs1000-anyone-used-anything-more-modern

[salty_monk]

Put a few thousand miles on that one.... The DL650 rear master also looked liked a good option but the one I used was easier to get, newer & cheaper...

[Shin-Ken 1074]

Yes, there are other brake master cylinder options you could adapt to suit you GS750. As an example I am working on a Suzuki project build and when it came to the rear brakes I looked at other Suzuki brakes for the build for 3 reasons:

1) Brake caliper and master cylinder for a 1981 Suzuki GSX1100 are expensive to buy new, OEM rebuild kits are NLA where I am and used brake parts for this model in my neck of the woods are usually in poor condition.

2) Needed lighter brake components for the build so it didn't matter what the brakes were from as long as they were lighter and could be adapted to the frame.

3) Availability of brake parts to future proof as well as having OEM rebuild kits at a reasonable price.

I used a 2005 GSX-R1000 rear caliper and master cylinder for the build, cheap to buy the parts used and Suzuki stock all parts needed for brake system. It wasn't a plug and play job and needed some planning, mods to the swing-arm for the caliper but the master cylinder bolted straight onto the original master cylinder mounting bracket after drilling new bolt holes. A bit of work but the end result was worth the effort:

lighter brakes
better brakes
OEM brake parts available at a reasonable price

2005 GSX-R 1000 Rear caliper fitted to a 1981 GSX 1100S
caliper by Max Mutarn, on Flickr


2005 GSX-R 1000 rear master cylinder fitted to a 1981 GSX1100S
RR 1 by Max Mutarn, on Flickr


Something to consider if you do go with another model rear master cylinder is the orientation of the brake line from the master cylinder. Sometimes luck is on your side and the stock line will fit however, in some cases you may have to have a brake line custom made to suit the banjo orientation from the master cylinder outlet, the brake line length, and the caliper banjo position.