Left Hand Rear Master Cylinder

Leonc · Jan 18, 2024

On my MK111, I have converted the bike to r/h gearchange (fairly simple) and set the the rear disc up to a l/h brake.
I purchased an Aliexpress 16mm master cylinder (NZD24), controlled by the pre 75 brake lever and cable through a custom hose. I have used this for several years and it performs well.
My issue is that the cylinder is designed for use in the horizontal plane and I have had to install it vertically for the cable to pull properly. Consequently is seeps a bit of fluid and periodically pulls air.
What I would like to do is repeat what I have seen on a few machines here, where the cylinder is mounted horizontally, using a pulling motion from behind the cable.
Unfortunately the configuration of the one I have is not suitable for this.
So the question is, what specific brand or bike application of horizontal master cylinder have people successfully used when doing this?
Thanks for any responses.

Ron L · Jan 19, 2024

It's not particularly elegant, but when I put a Mk3 disc rear wheel on my Mk2 Interstate I used a Brembo rear master cylinder with a remote reservoir. The master is cable operated and uses a simple bellcrank to convert the motion from pull to push. This was done over 15 years ago and the tools available to me at the time were files, drills, and a "death wheel" so it looks a little crude, but has been trouble free. I should add that I replaced the rear caliper with a 2 piston Brembo and smaller, lighter Brembo disc.

Leonc · Jan 19, 2024

Ron L said:
It's not particularly elegant, but when I put a Mk3 disc rear wheel on my Mk2 Interstate I used a Brembo rear master cylinder with a remote reservoir. The master is cable operated and uses a simple bellcrank to convert the motion from pull to push. This was done over 15 years ago and the tools available to me at the time were files, drills, and a "death wheel" so it looks a little crude, but has been trouble free. I should add that I replaced the rear caliper with a 2 piston Brembo and smaller, lighter Brembo disc.
View attachment 112183

Thanks for that.
I note that the cylinder is vertical as I have in mine, but you have not had any leaking issues.
Are you aware of the specific Brembo cylinder that you purchased?
Cheers

grandpaul · Jan 19, 2024

I converted my Dreer Prototype Monoshock MkIII to right-foot-shift, so I had to fab up a left foot brake setup, but I went direct because that's what I had to work with parts-wise. My tool selection was similar to @Ron L

ludwig · Jan 20, 2024

Probably not relevant for you, but mine is attached on 2 welded tabs .
( no Z plates):

You do not need a reservoir. 20 cm of cristal tube holds plenty of brake fluid.
Caution: DOT 4 will 'sweat' trough cristal tube. I use DOT 5 for the rear brake.

kommando · Jan 20, 2024

A seal should not leak regardless of orientation, get a quality rebuild kit or a better master cylinder. Aliexpress stuff is cheap for a reason.

Leonc · Jan 20, 2024

kommando said:
A seal should not leak regardless of orientation, get a quality rebuild kit or a better master cylinder. Aliexpress stuff is cheap for a reason.

Just to clarify, the reservoir hose entry into the body is where it seeps from, not the seal. The cheap cylinder was purchased as it was all a bit experimental for me.

Ron L · Jan 22, 2024

Leonc said:
Thanks for that.
I note that the cylinder is vertical as I have in mine, but you have not had any leaking issues.
Are you aware of the specific Brembo cylinder that you purchased?
Cheers

I don't recall the Brembo part number but is the same as those found on mid-90's Ducati 900 SS. I used the Ducati/Brembo remote reservoir and simply mounted it to the rear frame plate where I could easily fill it by removing the seat. The master cylinder should not leak from the reservoir tube or inlet spigot regardless of cylinder orientation.