I give up on this brake thing,help please

ok.81 xj 650.I have gone over this before.I am back because what I have done isn't working. I put on new pads, those and the caliper fit just fine over the disc. I like to never have gotten the old piston out.I had to use grease.I soaked and cleaned it sterile like nearly.I used all the replacement rubber seals I bought from len.They fit perfectly of course. I coated the piston with brake cleaner.I had to use a c clamp to get it started and after about 1/4 inch it went down easy the rest of the way with the clamp.I probably could have pushed it down by hand at that point. I put a new master cylinder on. it was new, clean untouched.I had the old one if I needed it.I used my mightvac to bleed the system.Clean fluid no bubbles after a few pumps.I used way over the amount of fluid needed to make sure.No lever.No brakes.I am sure now its because the piston is not moving.It has to move out to put pressure against the pads, and probably is just sitting still.Here is my next plan.Take the through bolt out of the caliper, and the nut on top.Pull it free of the rotor.Let the pads swing free.The master cylinder is full, so pump the lever.The piston should be coming out of its hole.If it doesn't then the piston is stuck somehow.I don't know if I take the piston back out, maybe hone the chamber a little? I don't want to take too much material off.If I do that and the piston starts going in without a clamp I figure that will do it. I have not found an easy way to get the piston out. summary: new pads, new seals,new master cylinder, new fluid, clean everywhere.Must be something causing the piston to stick.Input appreciated.obviously someone will say maybe its the new master cylinder, maybe it isn't applying enough fluid pressure.If I hadn't already tried 2 completely stock MC before I might agree.I rebuilt the stock master cylinder after through cleaning and installing new parts from len/chacal/xj4 ever.It didn't work either. I even bought a brand new piston, it didn't move either.

 

I had all kinds of trouble bleeding my system after a similar rebuild. Are you getting good feel from squeezing the lever? Is it firm or soft? If soft, that's a sign of air in the system. The trick is to use vibration to migrate air bubbles up the line and into the master cylinder. As others have recommended, using a palm sander and holding it against the components, starting from the bottom does the trick (no sand paper of course!).
Anyway, that's one avenue of attack.

(btw, this has a Matti reply waiting, I'm sure... )

 

so like take a sander to the outside of the piston?

 

You state all is new, but did you replace the 81 vintage brake hoses? or did you upgrade to braided stainless ( recommended ) Take a large syringe (meat injector works best) attached a short piece of clear hose to syringe and bleeder fill syringe with brake fluid. Open bleeder a slight amount ,push plunger of syringe till empty , close bleeder . Check master cylinder fluid will be pushed out of it so be careful , check and see if your lever has any resistance. If you have the dual disk you will need to do this on both sides . By doing this from bottom it should push fluid as well as bubbles out , it actually worked when ne man bleeder bit the dust.

 

I also taped the brake lever tight as possible to the handebar overnight and the brake was fine in the morning.

 

I've had more than one bike where air got trapped at the high point in the line, usually right where the banjo bolt is for the MC. This causes the lever to be really soft as if it was not pumping anything. If you are sure there is fluid in the caliper, try cracking the banjo bolt a little when pulling the lever. The trick is to open the bolt as you pull the lever and then close it just before the lever reaches the bars. I just finished up a Vulcan not too long ago where I had to do this for both the clutch and front brake as the MC's for both angled upward putting the bolt above the reservoir.

 

when I open the bleeder fluid comes out. No air. It is a single disc. No I did not replace the hoses. The parts bike had good brakes when I rolled it down the trailer several months ago. I have also tried its components on this bike. If the piston is not moving would it be then that the lever wouldn't budge? Instead of totally limp, as in no resistance at all? I am not giving up because the bike is rideable except it has no brakes. It has to be fixable, just haven't figured it out. But I do appreciate the help. My only experience is bleeding air out of a hydraulic master cylinder on the clutch side of a Yamaha. But the lever is not toally limp in that occasion. And after I got clear fluid coming out the lever got more and more firm. But not so with this one. The mightyvac gets air out much quicker than hand pumping. If fluid is coming out of the bleeder than fluid is coming out and around the piston, correct?

 

You can check if there is fluid behind the piston. Open the bleeder valve and push the piston back l am assuming it is not fully back now . If fluid is there it will be forced out of the valve. You can also try this before you open the bleeder valve if you want. Push the piston back and check if there is a slight increase in the master cylinder fluid level. If there is then you have the system full of fluid. But beware it could be invisible air in the fluid that will not operate the brake. To help get rid of this tie the brake lever as tight to the handlebar grip as you can overnight. I did that and brake was brilliant next morning. And l had used new fluid as you will be. I had the same problems as you have and it was invisible air bubbles that caused it. Good luck.

 

PS for want of a better term l mean tiny air bubbles that are invisible to the eye. Tying the brake lever to the handlebar overnight gets rid of them. I think you could have invisible air bubbles in your hydraulic system. You cannot see tiny air bubbles but if they are there you will have no pressure to push the caliper cylinder against the brake pad and disc.

 

You cannot see tiny air bubbles but if they are there you will have no pressure to push the caliper piston I meant against the brake pad and disc.

 

If there is any air in there, the lever can move full travel and the piston will not move at all. Been there done that. Highly doubtful that the piston is stuck considering you were able to install it during the rebuild.

Bleeding can be a frustrating thing. Simple concept but almost never goes that way, even for guys that have done it many times.

 

Here is problem with original rubber brake hoses they may look great on outside ,internally it may be collapsed.

 

Yes and the bikes are old now.

 

umm your supposed to use brake fluid. cleaner may be the problem

 

cruiserlover,

If those are the original brake lines, I would not trust my life to hard rubber 35 yr old brake lines......there has been a lot of technological advances in the last 35 yrs with regards to brake lines.....

Chacal has nice reinforced steel braided brake lines that are worth purchasing......your life is worth it.....

Just my thoughts....

 

oops.But after bleeding through 1/2 a bottle of brake fluid I think it would be gone though

 

I agree.2 small patches of rubber touching the road from my tires and the brakes are the utmost importance.I want the brakes to work first.Then I will replace the lines.The brakes should work even with old lines unless they were leaking and they aren't.is this correct? particularly if they worked before.

 

It is one of the most frustrating.Once the hoses have been off it is difficult to get it out.I used the mightyvac to make it easier, but no good so far.One question about that.The rubber connection from the mightyvac covers the bleeder valve.It will not work right if it doesnt. So I get the air out, then have to take the mightyvac connection loose then retighten the bleeder.That few seconds maybe lets air in.if i could reach up and hold the lever down while i get the mightvac fitting loose then tighten the valve maybe that would work.Perhaps?

 

I was thinking you melted the seals to the piston

 

Why go through the trouble your having in bleeding and replace the hoses AFTER ? Now is the best time agree 100% with 5 of a kind your life depends on this taking short cuts is not a good idea.

 

Sounds like the piston got hung up in the caliper bore. The piston is only reusable if it's not pitted with corrosion spots. Good used ones are way cheaper than new ones. Good used pistons can be sanded lightly then polished to look new. I chuck up caliper pistons with a small freeze plug and put them in the drill press to rejuvenate them. After sanding and polishing them up they look like mirrors.
The caliper bore can be honed to remove imperfections. Sanding with 600 grit sand paper also works.
There is a product made by Castrol called Red Rubber Grease, that is synthetic and compatible with brake fluid and used specifically on caliper pistons and M/C bores, that circumvents pistons from hanging up in thier bores and is perfect for coating caliper seals. Its spendy but worth the $$$.
Note...Dont use petroleum based or chassis grease on brake systems, period. The seals and rubber parts associated with brake systems arent compatible with petroleum based products. They will deform, swell and disintegrate then fail.

http://www.redrubbergrease.com

Without seals installed in the caliper the piston should easily slip into and out of the caliper bore with little to no pressure needed and no resistance either.
Grease the seals, bore and piston with caliper grease, chassis grease is not compatible with brake fluid, and everything should easily reassemble by hand without any tools.
Bench bleed your master cylinder before bleeding the system helps in the bleeding process. Also wrapping the bleeder screw threads with teflon tape, just the threads not the tapered end with the hole, does away with air bubbles that sneak past the threads while trying to perform brake bleeding.
You'll be amazed how easily and quickly the brakes bleed after following these steps, honestly.

I've been through the shit your going through long ago and its fixable so don't give up.
No short cuts either....
Good luck.

 

brake cleaner melts seals? I used inside the piston bore before the seal was installed, to clean out the chamber.I put some on the outside of the piston to make it slicker when I was putting it back in.Which it did not do. All total probably 2 o3 3 ml total used to coat the outside of the piston. I don't know.This really is aggravating.

 

Great information.I didn't know there was such thing as caliper grease.I used thick black grease and a grease gun to get the piston out.It took a lot of brake cleaner to get all that out.I feel like I got it out.I will try to get the piston out again.Take out the seal, see if the piston goes in and out easily then.I will try using some fine grit sandpaper on the piston.And the Teflon tape too on the screw.I have done numerous complete brake repair and replacements on autos.This should be easy.Nothing is cooperating.Once I got the piston out, cleaned all the grease out, I expected the piston to go in easily.The problem seemed to be that the piston was cocked at a slight angle and therefore did not want to go down in the hole.I tried both thumbs like if I was pushing a tappet in to no avail.The c clamp forced it down a little, the piston righted itself, and the rest of the way down went easily.

 

Sounds like your close to figuring this one out. Take your time, do it right, once.

 

Thanks.I appreciate everyone's input

 

says on my cans of brake cleaner no to spray rubber parts.
you sprayed the piston inserted and as the piston slid in the cleaner was wiped off by the seals could have swelled the seals.

did you test the MC with the a plug in the bolt hole? it is a allen bolt that chacal sells or you could use a bolt.
are you sure you installed the mc seals in the correct direction?

 

you do not want to sand the piston you want to hone the bore.

 

my brake cleaner isn't spray.it is in a bottle. the rubber seal will only go in 1 way.it fits perfectly in the groove. the one I bought off ebay was of course wrong.The only time I strayed from chacal. Cost me an extra $40. I have a metric bolt that screws into the hole where the hose would bolt to , to maintain pressure whether using air or grease. My air compressor goes up to 150 psi.With it maxed out, the hose hole bolt in place, applying the air nozzle over the bleeder valve the piston would not come out. With grease it does everytime. I think I need to hone the cylinder. I don't know how. Buy a wire brush and put it on my drill and run it in and out the bore a few times? if there is a brush the right size. I have seen them as small as a Dremel and as big as a cutoff tool. These bores are about 21 mm diameter it appears give or take.

 

I believe they are talking about something like this

you can fine them at auto shops, amazon, etc. Just search for "brake hone"

 

That depends on the condition of both.
Sometimes the piston will benefit from cleaning the surface up. Same goes for the bore. And sometimes neither will do any good.

 

if you can't get pressure on the lever your not putting pressure on the piston, it'll never move without a firm lever.
don't start with hones and sanding, you'll just mess it up.
just put your thumb over the outlet of the MC, you'll know if it's pumping. sometimes just bouncing the lever a little will get air that's stuck in the top fittings to come out the little hole in the MC. that little hole relieves the pressure on the piston so if you didn't get some squirt back from it, you never pushed on the piston.
if you have a bubble in the hose and you don't pump it down and out, as soon as it stops going down, it's going back up.
forget the tighten/loosen thing at the WC, when you squeeze more comes out than will get sucked back in, just work the lever
use teflon tape and think like a bubble

 

Today's winner of the internets.............

 

great information.Not sure what WC stands for, brake line at the caliper connection? I now will start thinking like a bubble. I have lots of good advice but that one is the best.

 

WC typically means water closet.
I think Polock meant MC - master cylinder, otherwise this post ends up in the Matti category.

 

On my planet WC is Wheel Cylinder not this
he thought about bubbles to long

 

well for sure it isn't water closet.thanks

 

For clarification, XJ550H is correct, your not actually sanding the piston to reduce the size or OD to make it fit. You are sanding or burnishing the piston in preparation for polishing to make it smooth. The sand paper you would use is 600 grit or higher which is only good for polishing prep.
The caliper can be lightly sanded prior to honing it to knock off the heavy deposits. The caliper can become pitted also which typically renders it useless.
The pistons and the caliper are two different types of metal that are basically in contact with each other. Dissimilar metal corrosion then comes into play along with extreme heating and cooling and also moisture. Add brake dust and road grime and you get a crappy environment within a system that needs to be sano to function correctly. This enviroment creates a corrosive layer on both metals which can be sanded or honed off to a point. It's the only way to remove it or buy better or new stuff.
We're not removing significant material, like boring out engine cylinders, just knocking off the surface corrosion that makes calipers hang up. The piston is easy, the caliper not so much but its worth a try if it isn't too far gone.

 

Being the piston was forced into the caliper with a c-clamp you'll need to remove it and figure why it's being such a bitch going in. You have a lot of advice and suggestions that have been tossed in your direction. Everyone is hopefully offering solutions based on real experience and not just what has been skimmed over during a casual read over morning coffee. It's your call, good luck and please share your fix when you beat this challenge.
Be the bubble, I guess.

 

If you pump the brake lever and get no resistance then one of three things is the problem. 1. Bad m/c; 2. Air in system; or, 3. leaking caliper/line. I am betting on #’s 1 or 2, favoring 2.

 

it is windy, flooding from too much rain, and 44 degrees.I pushed the bike from my nice garage to my back patio since it isnt rideable.Another week of this crappy weather. Someone posted a lot of information has been tossed my way.I am aware of that.I appreciate it.There are 2 problems.One is the list tabaka said.I agree 1 and 2.The next is larry mc comment.Why is the piston such a bitch going in.I have 2 calipers, 3 pistons, all 3 dont go in without using a clamp for the initial insertion.It is because pushing the piston in straight, not slightly uneven one side higher than the other I havent been able to dnce past that point it goes on down.However, pulling the piston back out should be easy based on that.And it isnt.So something is going on,.but i have all the advice i should need.I will get it figured out and post here when i do.I have rebuilt an entire gs 1000 engine before.This brake thing should be within my capabilities. So far its winning the battle.Tires and brakes are the only thing between me and safe operating the motorcycle. I am not leaving the driveway till I know this is 100% right.Thanks to everyone.

 

A sidenote trivial comment: I love the wheels, the inline narrow engine, the sort of square instruments, the teardrop sideview of the tank.This will be a great bike when i get it sorted out.

 

I like your spirit!

 

I just recently rebuilt the caliper on my XJ550, and like yours it was a BEAR to get the piston out. It was the corrosion in the seal grooves that swelled the seals and locked them to the piston.
I didn't see you mention in your posts that you methodically scraped the seal grooves zestfully clean (as Len likes to say) in the caliper, with something like dental picks. That's what worked for me. If you don't get all the aluminum corrosion out of the grooves that prevented the piston from coming out easily to begin with, it's not going to go back in easily, or move properly during braking.
I didn't reuse the piston, but bought a NOS piston and seals kit from my old-school, hole-in-the-wall Yamaha shop. But my new piston went in by hand (without a c-clamp) after coating with brake fluid.
Regarding the piston not moving for you now, it's definitely a bleeding problem. If you can pull the brake lever all the way to the grip, you're not bled (or your lever's out of adjustment).
Bleeding the XJs is DEFINITELY a pain in the butt, no question. It was the hardest and most time-consuming part of my rebuild.

 

great input seca.I just posted all of it for sale.I need to get out of my house asap.I need this stuff gone. In our for sale section.2 bikes for low price.

 

You never want to use brake cleaner on the "rubber" parts. The parts are not compatible and will swell or breakdown, possibly get sticky. When I bled my xj750 brakes I used a syringe to force the fluid up through the system using the bleeder valve. Rock hard brake handle after that.