How to clean up your S.O.H.C. Caliper

Many people email or call and some have the same problems, so I thought I might do a wee bit of a blog and show you what we do when you grab an old CB750 and fnd out that the front brake sticks and wont release, how can you over come this and get the old girl to function again.


Now- this is my way, someone else may in fact do theirs differently, but this is what I taught myself and so far it has helped me so many times and i did it all at the shop with a minimum of tools too.


As you can see, this one was nasty and to be honest, most of them are like this, but if you cannot even get the brake pad out, sometimes- if you are lucky, if you remove the brake hose and eave the bleed nipple closed, you can try and blow the thing out with compressed air.

But remember if you are going to do that, wear safety glasses and put the caliper in a bucket with a towel in it, as if that brake pad and piston comes out, it will be traveling faster than your bike can go, so make sure you have a safe area to do this.

Now, if like me, the bugger is stuck in there like a fat foot in a thing shoe, then the only real way to remove the brake pad and piston is to do what we do.



Get an old pair of handlebars and fit a working master Cylinder to the bars, then simply just bleed the caliper until fluid comes out of the bleed nipple, tighten off and then check the master cylinder for fluid, top off and screw the lid back on and start to pump the brake lever.

If you have bled the caliper the piston WILL start to move and slowly the brake pad will simply plop out, but- keep checking on the brake fluid as you will soon run out and don’t want an air blockage.


Fill reservoir with brake fluid and keep pumping and make sure that you have at least a towel under the caliper body as when the piston pops out, of course, all the fluid is going to be right behind it.

Plus the old fluid will be dirty and many times all gummed up and this makes a mess, so a towel is always a good thing, make sure you throw the towel away after as you dont want to use it for cleaning a freshly painted gas tank as brake fluid is brutal on paint.


Now the brake pad and caliper is out, you will see just how bad the piston has become, the main factor for this is that the Caliper body is aluminum and the Piston is steel, the steel sweats and then rusts and then it turns into pitting, thus when you press the brake, the pitts will catch against the seal and wont return and the brake sticks on, that’s why sometimes, if you have moved an old bike and the brake sticks and then you see the old boy who owned the bike, kick the caliper, its enough force to pop the piston back home but will always stick.


So, we now manufacture a Stainless steel piston to prevent this from happening again and we use them all the time.




Check our parts page out as we sell a reaming kit now to get the Caliper looking good and smooth.

I use a dremel and a rubber wheel and then I gently remove any of the oxidization around the caliper with the rubber wheel, but not harming the aluminum, this works very well and I must of done this to over 150 Calipers over the years.

It gets hot  on the caliper body but this is so worth it and you will be surprised at the end result to be honest.

But once you dremel the body, it will be nice and smooth, I clean her out with lacquer thinner and air dry, then fit a New Rubber seal in its groove, i usually dip it in brake fluid and fit, then use our Stainless Steel piston and put a little brake fluid on that and it will plop in the caliper nice and smoothly.

Then simply add your brake pads and then fit to the caliper bracket on your machine, just bleed the brake and you are done.

We sell the brake bleeders too and the Rubber seals, so we have ya covered with it all, as well as the brake lines too.

Now if you would like a little more insight, I made three videos with my little camera today, so check them out as these may help you as you go along with your brake rebuild.

Part 2