Brakes Breaking

Hi all,

Pardon the pun above. I have had this issue ever since I got my bike - sticky brakes.

After bleeding, cleaning the return hole, and replacing the brake line itself, I still can not fix this issue.

My only guess now is that I will either need to clean or rebuild my master cylinder.

I'm pretty sure that it's not the caliper because whenever my brakes stick, I can relieve the pressure through the bleeder valve on the side of the road, and bam, a nice feeling brake lever and no more sticky brakes.

Also, whenever I had the '81 lines on the bike, the return hole would fill up with little tiny pieces of rubber hose, blocking the return hole and causing the issue.

As per usual, I have essentially two questions:

1. It is the master cylinder, right?
2. What can I do to solve this issue? Is it worth a rebuild or should I try a good cleaning first?

 

Sounds like m/c guts failure. If it's never been rebuilt it's way past due.

Gary H.

 

rebuild the caliper too
those little tiny pieces of rubber hose are also down in the caliper
really nice rebuild kit 39.99 take a look
YAMAHA NOS XJ550 750 XS1100 1981-84, FRNT BRAKE PAD KIT, 23W-W0045-01-00 #100

it is for maxim but it is the shim plate for the back of the pad that makes the difference if you still have the old one no problem

 

I agree. Rebuild everything, and I would consider new brake lines since you know you have bits of rubber floating around.

 

If it's not relieving pressure without you hitting the bleeder, it's probably the MC. However, for the cost of it, as well as the ease of mind, wouldn't you just spend a few bucks for a MC and Caliper rebuild kit? And maybe some new hoses while you're at it...

 

Ok,

I just spent lots of money to get three things.

1. K&L Master Cylinder Rebuild Kit
2. K&L Caliper Rebuild Kit
3. Yamaha NOS Front Brake Pad Kit

Thanks for your advice, guys.

EDIT:
Yes, I already replaced the brake line. It's the Goodridge universal one with banjo fittings.

 

It might seem like lotsa money. But personally, I wouldn't wanna end up as raspberry jam on someone's bumper cuz of 39.95

 

I would be sure to flush the fuel line with clean brake fluid just to make sure you get and rubber bits out.

 

and flush the brake line with gasoline

 

So I have a little problem...

I'm pretty sure that the MC rebuild kit I bought doesn't work. Whenever I try to bleed the system, it doesn't advance. It just pushes then pulls back the same amount.

I've tried just about everything in the book, but nothing works. I bet that if I put the original plunger back in, I could bleed out all the air in 5 minutes and have my sticking brakes back, but that's no good...

What should I do before buying a new MC?

 

Are you sure the kit is the correct diameter for the bore? Are you fully closing the bleeder screw before you let off the handle?

Gary H.

 

While I haven't measured the exact diameter, it seems like an exact match, and the ebay listing specifically says XJ550 Seca of all kinds, as well as a lot of other Yamahas.


And yes, I am sure I am bleeding them correctly. I've done it 4 times before on XJ550's.

EDIT:

Yeah the master cylinder had never been rebuilt. I could build a mountain out of all that rust. I'd upload a photo but I think you get the picture.

 

orings correctly oriented. proper location
did you clean out the little holes from res to plunger
hone the cylinder ?

 

What do you mean by "Origins correctly oriented," this may be my problem. Do I need to rotate the plunger?

I did clean the holes, and I have been since I got the bike. The rust from the original plunger was seeping up into the holes and clogging them, I think.

Also not sure what you mean by "hone the cylinder."

But I think you may have the solution.

 

Are you saying that when you pull the handle fluid doesn't exit the bleeder screw? Are the banjo bolts clean and clear of debris?

Gary H.

 

Sorry that was a little unclear.
The fluid does exit the bleeder valve, however...

Once I close the valve, release the lever, pull the lever, and open the valve again, it just sucks back up, or does't move at all.

 

the orings go on in a certain direction on the plunger

hone take a small dowel and wrap 1000 grit wet dry sand paper on it put in a drill and run it in and out a few times to clean the walls.
wet it with brake fluid

 

Oh, yes, I'm about 80% sure that I got the o rings on in the right order. I even had to reinstall one because it was on the wrong way. I used the original as a model.

And no, I didn't sand the bore. It actually looked pretty clean even though the plunger was so nasty. I might have to do that though.

 

try a little teflon tape on the bleeder screw the threads may be a bit sloppy.

http://www.xjbikes.com/forums/threads/master-cylinder-fails-to-pump.48360/#post-430015

 

Ah, I've heard of that, but never tried it. It's very possible since I've used it so much.

 

read the link i posted good info

 

Well, sorry to keep bumping this old thread, but I'm going to try and reuse the old plunger.

The K&L one doesn't work so good, I'm about 90% sure it's the problem.

The old one looks like lead, but it's now pretty much clean on the internal part since I gave it a good scrubbing with a wire brush.

The external part is a little bit pitted with rust but I don't think that will be an issue.

And more o-rings are on the way since I broke both of the center ones

But should I keep the old one?

I think the gunky buildup on the plunger was actually causing the issue, rather than the plunger itself.

 

if the plunger works use it
fluid flows around the plunger if gunked up thats was a problem

 

Gotcha. That makes so much sense.

 

I just honed the bore on my m/c yesterday and I discovered that 0000 steel wool with the dowel and drill works excellent. Just be sure to blow it out real good before reassembly

 

What he ^ said.

Gary H.

 

I give up. Even the old plunger doesn't work anymore.

A new master cylinder is on the way...

But, what could have caused this?

It's not the return hole which is my only guess.

 

I am looking for a 550 mc if your done with yours start a conversation with me

 

Alright, I got the new master cylinder, but it's not working 100%.

I can feel a delay in the lever, as in it takes about 15% before the brakes kick in.

I can feel the brake piston advancing before pressing the brake pads against the rotor if I put my fingers on the bottom of the brake pad.

It's like the opposite of what I had before...

Any ideas?

 

Don't know if i've got this right, but it sounds like your calipers seized (the sliding bolts). You can remove the pads and check that it moves freely.