master cylinder piston

[colebrooker]

This might be a simple question but how does the piston assembly of the front brake cylinder come out. It's the square type and I am trying to clean it all as the bike has not been used for a couple of years. The basic problem is the brake sometimes will not release fully. It needs a release of pressure at the bleed nipple each time. The bottom of the reservoir was gungy. Thanks.

 

[5twins]

A snap ring holds it in.

 

[colebrooker]

Thanks 5twins, so it just needs a thin lever to spring it out of the groove?

 

[5twins]

Snap ring pliers work best. MikesXS has a special long nose pair that's angled 90° on the end. This is a real, internal snap ring like so .....

..... not just a wire ring you would pry out. You'll want snap ring pliers or long needle nose with a real pointy end.

 

[BigBoreSwede]

Hello.

Be careful when dissassemble the master cylinder. It´s kind of sensetive. Once all part are out, take a good look in any wear is visible. If so....get new seals and stuff. It´s so boring to put a master cylinder back together realizing it´s not working alright.

/BigBoreSwede

 

[gggGary]

Have you removed, disassembled, and cleaned the caliper also? There are two ports between the reservoir and the piston on the master cylinder, the second port is very small. Once the piston is out a fine wire will clean that second port.

 

[colebrooker]

Thanks for the tips, I still have it all to do so it's all useful information.

 

[colebrooker]

gggGary, I have tried a fine wire on the second port without succes. It doesn't seem to be drilled through. My finest drill is 0.5mm is this too big?

 

[gggGary]

Well I think in inches but most likely yes that's too big. I think I use a single wire from some stranded copper electrical wire as a cleaner. I'll try to find a dimension. Believe it or not, I sharpen stainless safety wire on a grinder as a small hole cleaner. Sometimes putting a 90 in fine wire and pushing up from the piston side is necessary as a chunk from reservoir crud has the hole plugged.

 

[gggGary]

I used a wire from a fine wire wheel. it measured .32mm and fit in the hole with what seemed like a little to spare. If you haven't already, I carve the plastic tab out of the way with a utility knife.

 

[colebrooker]

gggGary, the second port on my mc definately was not drilled through or blocked. The metal is quite thick and there was no small hole. I have now drilled through with a .030 inch drill and all cleaned, caliper and piston all fine, refilled and bled. Seems good, time will tell if brake is going to drag again. It is a 14mm set. Thanks for your advice.

 

[gggGary]

Leaving this thread hanging has been bothering me so after a few tries I finally got a decent pic.



This hole was drilled by the factory. I am somewhat worried that you drilled a hole in an MC that did not have one......
You know the famous I heard it was true on the internet....

 

[colebrooker]

gggGary, thanks for your concern. Now i know what you meant by the plastic tab. Mine is not like this as it is the rectangular shape MC. The 2 ports are similar in that the 2nd was drilled part way through only. The hole i have put through here is only 30thou and can easily be blocked off if required. So far only done 20miles and the brake seems normal. Before it was as though the pressure was not releasing every time. It could be that a strip and clean solved the problem anyway.

I'm past learning age but there's still plenty out there.

 

[xjwmx]

I'm pretty sure everybody here would advise you to get a replacement master cylinder. I just wouldn't have brakes that weren't completely understandable....

 

[gggGary]

I tossed up an overall pic of the MC I was referring to, note it is "rectangular" compared to the early "round" ones, what you have is aftermarket? In my somewhat limited experience all the MCs I have worked on (20 or 30 on various jap bikes) have two ports. And the small port being plugged has been the cause of braking issues a fair number of times for me. So I am really wondering what is (was) up with yours? A pic of yours?

 

[colebrooker]

gggG, I have taken a couple of pics, here they are if I have done it properly. I haven't uploaded pics before.

 

[colebrooker]

I'll try again another day.

 

[colebrooker]

gggGary, another attempt at uploading a couple of pics of my MC.

 

[gggGary]

Hey you did it. What year is that on I haven't seen one quite like that, but I think it was Jayal just mentioned one made like that in a different thread. does it have a plate with two phillips head screws that holds the plastic in place? I think you did right drilling the hole, I did look around and the small compensation port is a part of every master cylinder diagram I found MC OR automotive. So I wonder how long those front brakes have been out to lunch????

 

[xjwmx]

When I first got my bike the hole in the caliper bleed screw was so gunked up and hardened it appeared like it never had the hole drilled.