Front Brakes

I just did the front brakes on my xj 750, the left side caliper piston moved freely back into the caliper, but the right side caliper piston did not want to go back into the caliper. I forced and forced it back almost all the way and replaced with new pads. When I put the caliper back on the bike I also had to force it on. When I took it for a ride the fron brake was dragging severely, knowing this I kept riding a few more miles hoping it would force the piston back into the caliper. I also bled all of the old fluid out of the system, and I noticed that in the master cylinder that was "crud" in there. My question is what do I do to fix this problem rebuild the caliper? master cylinder?



Thanks

 

If you got "The Mud-Crud" in the Master. Go for a complete Overhaul if you are putting your life on good working Front Brakes.

You'll get everything you need to do the Master when you order a Kit.
New Caliper Seals are surprisingly easy to fit.

It's the CLEANING-UP Process that's the most important. Restoring "Travel" to the MOVING PARTS on the caliper.

 

I'm having a similar problem on my XJ750 after putting stainless lines on the bike from Paragon Performance. I also had some crud in the master cylinder reservoir which I thought I sucked out. It looked like tiny pieces of the brake lines which is why I changed the lines out.

My next step is tear down the master cylinder and see what the parts look like inside. My guess is you are having the same problems I am:
1. Caliper needing cleaned & rebuilt
2. Pressure release hole could be blocked inside master cylinder.
Rebuild kits for the master cylinder and caliper are available but you may need a special set of pliers to get the circlip out of the master cylinder. see here: http://www.z1enterprises.com/catalog.as ... 0-1983-WB0

If you need new lines, these guys are great to deal with.
http://www.paragonperformance.com/Yamaha%20XJ.html

 

I had this problem too. Since the left caliper will return it may not be the master cylinder. But I would heed Rick's advice by all means. Mine were sticking due to gummed up caliper pistons. easy fix is to pump the piston out just before it comes out and clean with "Brake Kleen". Push the piston back in and reinstall caliper. If that doesn't work then the piston needs to be removed and the seals replaced.

 

its weird because one caliper works fine, but the other one sticks

 

Impulse2K1, I just finished rebuilding the master cylinder and one caliper on my XJ. The amount of crud inside the master cylinder was amazing. So if your reservoir had crud, I'm sure the inside does too. Don't forget the use a very small piece of wire to clean out the pressure relief hole. I use 1 strand of a piece of multi-strand speaker wire. The hole you need to clean out looks like some one started to drill a 1/8" hole but then stopped. The tiny hole is in the center of that.

BTW, using a 12 gauge shotgun barrel brush work very well at cleaning the inside of the master cylinder.

You don't NEED a special set of plier to get that circlip out. I used long thin needle nose plier and modified the ends with my bench grinder. After swearing a few times, it came out.

If one of your caliper pistons can't be pushed back in by hand, you need to re-clean or re-check your rubber o-rings. Did you use a piece of scotch bright to clean the piston? Make that thing shine before putting it back together. The 3M white scotch bright is the finner grade and will make a nice shine with out scratching. Using a little brake fluid as lube will help the piston go back in smoothly.

 

When you get ready to put the Caliper Piston back in ... lube the bore, the new seals and the outside of the Piston with some clean, fresh -- brake fluid.

The Piston needs to be SQUARED-UP and PLUMB for pushing it back into the caliper.

A C-clamp, a Socket and a two Fender Washers make this job as simple as can be.

Wrap one of the Fender Washers in Duct Tape. Use that one to protect the Outside of the Caliper from being marred by the C-clamp.

Place the largest socket you have that will fit inside the Piston and tape the other washer over the square opening.
Now ... Position the Clamp on the Washer taped to the Socket and the taped-up washer over the Logo on the Caliper and tighten the Clamp while keeping the Piston lined-up while you tighten the Clamp.

Lube the outside of the Piston and tighten-up the Clamp. The Piston will be pressed-in quite easily.

. . . . . . . . . . . . . . . . . . . . . .

Once you have the Piston "Started" ... you can also:

Fill the Caliper with some clean, fresh, brake fluid ... and "Bench Bleed" the Caliper as you press the Piston back in.
Use the Bleed Nipple and a correct fitting bolt to prevent the fluid from leaking-out until you've mounted the Caliper and are ready to re-connect the Banjo Fitting on the Brake Line. This is a real time saver if you don't have a vacuum assisted brake bleeding system.

 

awesome thanks guys

 

i replaced my brake pads and completely flushed the brake lines, i am 99.9% sure that all the air is out, yet my brakes still work very poorly and are really squishy. I can pump them up and they get tighter but eventually soften up again, could this mean i just need to clean the master cylinder, do i need to buy a rebuild kit or am i doing something wrong?

 

Sounds like you still have some hidden air in the system. A way to speed things up is to use a vacuum bleeder. A vacuum bleeder pulls the fluid through the system from the bottm side(the caliper). And pulls the air out along with it. You may want a helper to pour fluid in the master while bleeding. It goes fast.

 

Since your life may depend on it ... Brake Master Rebuild Kit.

I know you bled them for awhile.
The fact that you can pump-'em-up a bit is SCREAMING Master Cylinder Seals.

Just do it and be safe.
Buy yourself a One-way bleeder hose and an Ear Syringe to make the job easy.
Suck-out all the crap in the Master.
Clean it.
Stick the kit in it there ... and bleed-'em out.
Theen, when you need a handful of front brakes ... you'll have a whole handful!

 

Definately GOOD sound advice.

 

o yeah, when i have the lid off the cylinder and i pump the brakes, if enough fluid is forced into the lines, it will spurt a little back up out of hole which is sucks the fluid through. Is this a sure sign that the seals are shot or something of that manner?

 

Hello everyone im going to jump in here a little late..

This is the deal I have the calipers apart ...Im now in the process of getting them back together..Thing is ,I have this bag of grease that came with the seal set!
im thinking grease up the piston and the seals so this is what I have done.

Is this correct..I have to admit the brake fluid on the seals is a good piece of advice, but im just wondering what the fluid is going to do to the grease I have put all in the caliper and on the seals..Once again this is grease that came with the seal set!

Do I need to redo this step? I have cleaned and scrubed these things to a cleaness.. I dont want to do it again.. so before I put the pistons back in Ill ask these questions..Thanx for your help, sorry im a little late on the subject.Ridz

 

ridz:

If you have sliding parts, a traveling or floating caliper ... that's what gets greased.

Otherwise ... lube it with lots of clean brake fluid as you replace the seals, install the piston and finish-up the job.

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xjyamaha:

Yes! Having your own miniature "Old Faithful" spouting-up from the Master Cylinder reservoir is the Smokin' Gun you need to overhaul the Master and toss a Kit in there.

 

Sounds like thies guys know more about brakes than I do, but I had the same problem with my xj 650 , I could not get one of the caliper cylinders to go back in , I just bled and flusyed the break lines (careful not to let any air in) and the cylinder pushed back in easily while bleeding (no back prssure pushing it out ) . hope this is helpful

Dave

 

i had a quick Q on brakes, i completely rebuilt the caliper on my 650, new pads and seals with a good cleaning, then i cleaned my master cylinder, pretty gunky, but i got it spotless. I put everything back together and pumped fresh fluid through for what seems like an hour and they still feel kinda spongy, if i pump the shit outta them they get nice and tight but it seems like they soften slightly after a bit. I cant see how it's possible to still have air in the lines, i dont see bubbles anymore and i pumped um for an hour? Any suggestions

 

This is the Classic symptom for Master Cylinder Seals being worn-out and not able to provide adequite pressure.
Instead of forcing the brake fluid down the lines ... they seep and no real pressure is formed. The Master Cylinder usually shoots a stream of fluid up from within itself displaying that the fluid isn't being pumped by the pressure seal.