Introduction
As it’s a Saturday, I decided to spend some time cleaning up the two rear brake cylinders, remove rust, and use the honing tool to polish the inside of the left rear brake cylinder. I also decided that I should clean up all the components that make up each brake cylinder, below are the parts from the left rear brake cylinder (which is the newer of the two).
I ended up spending hours removing rust from the outside of the cylinders and right now my hands and fingers feel quite numb. I used a combination of a drill with a small wire circular brush attached, and wore safety goggles to protect my eyes from flying rust/wire.
I should have worn a face mask to keep the dust out of my mouth/nose but I didn’t have one handy. I can still taste the rust in my mouth, yuk.
Honing the rear left brake cylinder
I started by working on the recently removed left brake cylinder. It was not as bad shape as the rear right brake cylinder and I think that is because it (the entire brake cylinder) was replaced probably some time in the 1980’s. The pistons came straight out, no need for any additional work to remove them, that was a relief.
However there was a lot of surface rust on the ‘lip’ of the dust seal particularly on one side, so that would have to be removed with some sandpaper and brake fluid for lubrication.
I started with the honing tool, and poured some old brake fluid into the cylinder to aid with lubrication, the tool itself is simple, but the two brushes have a tendency to go flying if you are not careful.
After honing it for a while I got a nice result. Time to sand the dust seal lips. 
To get the rust off I spent probably at least an hour on this cylinder, finely sanding until most of the visible rust was gone.
I sanded by hand with 150 grit sand paper lubricated with brake fluid. The results were quite something, take a look.
After getting this brake cylinder looking so good I decided to do the same job on the other one, so out with more sandpaper and brake fluid, my poor fingers.
In addition to sanding the dust seal ‘lips’ I used the drill+circular wire brush to clean up as much surface rust on the outside of each cylinder as I could.
The end result of that is pretty shiny looking brake cylinders.
At this point they are starting to look much better.
The steel piston bars that pushes the pistons in were very rusty, so I cleaned them up with the circular wire brush connected to the electric drill, below you can see one that is clean versus one that was not worked on yet.
Note: You should wear protective eye glasses when working with wire brushes, the speed of the drill is so fast that bits of wire will fling off and can penetrate your eyeball if you are not careful.
The pistons inside it definitely look newer than the other ones and don’t have the markings found in the normal pistons. Below you can see two cleaned bars, and the newer pistons from the left rear brake cylinder. One of the two is clearly rusty, so here’s the before shot.
And here, is the after shot.
I was so impressed with the results that I continued cleaning all the bits (pistons, piston bars)
and then I checked/cleaned the rubber seals used to protect the pistons from dust, I also cleaned the inner spring which has two hard plastic bits on each end (comes off easily for cleaning) and removed any surface rust from the springs.
Below is the right rear brake cylinder and associated parts, if you are not impressed with the photo below click here to see what it looked like before I started working on it.
And here is the left most brake cylinder and it’s parts.
I then put all the bits back together again, just to see how it all looked.
I have to say, I’m impressed with the results !
Two cylinders done, 5 to go (including the brake master cylinder).
I did some research and found that you can still buy rear cylinders ‘new’ from the following link, not cheap but if you need one at least there’s a possibility of buying them.
Rear brake cylinder – http://shop.millermbz.com/brakes/rear-wheel-cylinder/26-0040
There may even be more parts available via the following link.