Stuck Rear Master Brake Cyl Yam RD

Hey guys...

Long story short...my rear brake cylinder seems be stuck.
I rebuilt my brake shoe with new seals.

The steel arm that actuates the brake pump in the rear doesnt even actuate,is there a way to repair/rebuild that master?

I guess theres corrosion in there causing the caliper to be stuck.
The dust cap is torn,the caliper doesnt leak.

I see three options:

1.)buy a STOCK maybe rebuild RD master cyl

2.)buy a rebuild kit (probably Yambits,around 60 dollars) and go to town

3.)buy a NEW master from e.g. a Yam R1 with a 5/8 sized caliper and modify it.

Do you guys know any 'new' brake pumps that work the way the RD does?

It has a steel arm that pumps from down to the downside of the brake pump.

Help appreciated.

Thanks in advance!

take it apart and see if it is too badly done to put a kit in

I will go for that!

Do you have an idea how to disassemble that pump?
I just see a nut on the side where the hose from the brake fluid reservoir goes and nothing else.
Where does corrosion normally build up in these?

underneath the torn rubber shaft boot there should be a snap ring,they can be tricky to remove but that should be all that holds it together
clean it up and get a look inside where the seal rides

as far as corrosion anywhaere that is exposed to water which could be inside and out, as brake fluid absorbs watr

xb33bsa said:

underneath the torn rubber shaft boot there should be a snap ring,they can be tricky to remove but that should be all that holds it together
clean it up and get a look inside where the seal rides

Click to expand...

There seems to be a outter rubber 'dust cap' and a seal around the piston that gets pushed in by the rod.

So i guess the trick is to get the snap ring off without tearing the seal boot.

The brake pump was sitting for quite i while just with a rag stuffed in so i guess water got in the system and corroded.

it is torn rip it out git r done too many qeustions ;D

you need to learn to think for yourself

^+1 ☺

So xb....

Just took the master out and used some wd40 to clean it out a lil bit,opened up the side feed where it has this strange nut (looks like copper).
Had a little but of gunk inside and after wobbling and trying the pump got goi g again,doesnt leak too....

Then i reinstalled it and tried to bleed the brake system....IMPOSSIBLE....

I used my vacuum brake bleeder whicb normally needs like 2min....didnt work...

Cant get the air out of my rear brake shoe.

So i though maybe cuz of its odd position (airbubble in the brakeshoe).

Demounted it and laid it on the table...had a little brake fluid coming out but with a LOT of air... after 30mins i gave up....

Do you have any idea how to bleed that system?

I tried too to bleed the master and then the brake shoe....didnt help.....

they are VERY simple to bleed
you can't use wd40 on a brake system or any thing oily
you will need a seal rebuild kit

Just checked again for a rebuild kit...50 euros....too expensive.

I think i m gonna go for a 'new' brake pump from ebay and modify it to fit my setup...just checked...yamaha r6 master costs 30 euros...

Do you know any newer motos running 5/8 rear pumps,or any ressource?

Thx for helping.

why don't you take yours apart and inspect the seals you may not have ruined them ? they are very simple to work on
you are making a simple situation difficult, why ?

Sorry for being a novice to brake pumps...didnt tear into that region that far.

When it comes to taking things apart i like to ask highly experienced people like you before i start digging.

I ll let you know when i took that sucker apart.

you can do it !

xb33bsa said:

it is torn rip it out git r done too many qeustions ;D

you need to learn to think for yourself

Click to expand...

I'm still at the question asking stage but you still help me! You secretly love everyone here


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1sttimer said:

I'm still at the question asking stage but you still help me! You secretly love everyone here


Sent from my iPhone using Tapatalk

Click to expand...

Xb is like the grumpy wise father i never had


Yes i guess theres a love/hate relationship.

Before you give up on it, try this. Remove the brake line at the master cylinder (pump). Put a finger tightly over the threaded hole and pump the cylinder carefully. Put a lot of rags around everywhere because brake fluid is very unfriendly to just about everything. If you get pressure, stroke the pump a couple of times to get any air out. You will not be able to keep brake fluid from squirting out, but you will be able to keep air from getting sucked back in. You can empty the reservoir very rapidly so be careful. The master cylinder should be completely full after this, so re-install the brake line, and then take the line free from the caliper. Block the open end tightly with your finger(s) and carefully pump the master cylinder. If it is working, you should be able to fill the line easily. Then put the caliper back on the bike, and put the line back on. Be careful to keep the line full by keeping it as high as possible until the last second before you reconnect it.
You should have no problem bleeding the air out of the caliper after that.

Most of the time that brakes are hard (or impossible) to bleed is because there is air trapped in the master cylinder (pump) right at the piston. If the line is attached- even if it has fluid in it, the air bubble just moves back and forth with the piston, so no fluid comes in. Taking the line off right there lets that critical air bubble out and once the piston starts pumping fluid, the problems are usually over. Often just cracking the fitting there to bleed out the air is enough to get things going.

In my experience, it is pretty rare for the master cylinder to actually give up working entirely. Usually they leak long before they stop pumping effectively.

Thank you moeb i will definitely try that!!!

I m actually was wondering why the master doesnt leak.

The rubber boot,as you can see in the pic, was totally shredded.

Is this the seal that holds the fluid in the master or is the actual seal behind the snap ring?
The inside of the pump looks brown and gooky is there a way to clean it without taking it apart,i m afraid that i could break the seal...

That torn rubber bit is just a dust seal. Most just fit into a groove just inside the opening. You probably can just pull it out of there and forget about it. Clean it up with some WD-40 and cotton swabs. It mounts upside down, so if you inspect and clean it once in a while it will likely be fine. If it is crusty in there you can take it apart and clean it up, but the problem is that, assuming it works, dis-assembly will drag the hydraulic seal past the crust and possibly damage it. So if it works, I would simply use it without the dust cover. Once you pull out the dust cover, you should see a snap ring that holds everything together. If you get it pretty clean, you can remove the snap ring and take it apart. There is not much inside. Most have just a piston with the seal on it, maybe a washer or plate to keep the seal shaped correctly and a spring with maybe a washer or two to keep it in place properly. Very simple, but pay very close attention to the order and orientation of each part because it may not be obvious at all how the parts are supposed to go. Also, there are a LOT of tiny variations in master cylinders, and often totally different parts in rebuild kits even though the parts can be used. Often I will hone the bore a bit with some #600 wet sandpaper wrapped around a wood dowel and submerged in brake fluid. I just do this by hand and only lightly and try to only concentrate on the outer areas that have corrosion. I have done quite a few this way and they have worked fine with no leaking or failures and no new parts. However, I have thrown many into the trash too, so it is a judgement call.

Hey moeb...

Today i tried what you told me to do.
I wrapped a rag around the open master cylinder...put my finger over the threaded hole on top of the master cylinder where the banjo bolt goes in.
Worked fine...as you said the master was full of fluid.
I kept the pedal compressed in order to keep air from getting sucked in.
Then i installed the line (line went from master to my hand,i dissconnected it from the caliper).
I pumped the pedal carefully having both my fingers closing the ring formed end with the tiny hole in the middle that goes on the banjo bolt on the caliper....

Nothing.

Then i tried again and i achieved that fluid came out but with air 'whistling' trough when i let of with my finger.

Then i put the hose of my vacuum brake bleeder on the one side of the ring formed piece of the line and my finger on the other....didnt suck anything out of that DARN line....

Is it possible that the master doesnt produce enough pressure to bleed the line?

The lines do no leak.i cant see anywhere they would suck air.

Thank you for your help!