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Discussion Starter #1
Hey guys! I'm new here, and I just got a ZR-7. I've been putting some work into it, and noticed that the right fork was leaking, no problem I fixed it.
Now here's where the problem arises: as I was putting the wheel back on and the calipers had closed slightly, so I pushed them apart, it was a little difficult opening them.
Since I was already messing with my brakes, I decided to bleed them. Now, they don't work. Before I replaced the fork, they were some of the most responsive breaks I've ever ridden on. What's the problem? Thanks in advance
-Gingy
 

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open up the bleed nipples and move the pistons back, check the calipers are moving freely on the slide pins, if not clean and regrease them.
then bleed the calliper's , that should reseat them in the right place.
then top-up fluid to the correct level.

welcome to the forum by the way :)
 

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youve probably got an air bubble in the master..or youve hyd locked it....

start by pulling the res cap off and SLOWLY pumping the lever and the brakes may come back.....as i had the same thing happen to me when i did the bearings and id simply hyd locked the master....if they do not youve got a BIG bubble in the system and it needs to be bleed...honestly if its doing this tho..id drain it clean it all out and refill and bleed..starting with bleeding the master first and the calipers last
 

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I did mine this spring as they were hanging up...Big C clamp pushed pistons in till they stopped moving...
Took a hose and got the brake fluid out of the master cyl..Filled it with fresh..Opened up the bleeder on one caliper with the cap off the master and let it gravity bleed untill clean fluid came out..Did the other side making sure to keep the master topped off with fluid...Then pumped them up and bled each side the correct way alternating untill I was sure there was no air in the system...
 

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Discussion Starter #5
Thanks for all the helpful replies! It ended up being air that was still in the line. I re-bled the system, and let it sit for a few hours, saw some pretty big bubbles come from the master cyl.
They are working good as new now. This is a really helpful community, I'll be here for a while.
 

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Welcome Gingy, glad it's fixed. Any other questions, or if you do any "mods", etc., please post. We, like children, like pictures too. Since our bike is no longer produced, and was fairly limited in production, it's good to see someone else keeping one "on the road". Lots of info here, both "on-line" and helpful members on this forum.
 
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I am stuck with dead front brakes as well now :( Here is what happened:

I noticed that the rubber brake piston seals were sticking out in a couple of places so I ordered brake caliper seal kits and decided to jump in and clean the calipers and pistons and replace the seals. This is the first time I am doing something like this, but after studying the manual and looking at some youtube videos I figured it should be pretty easy. I removed the calipers from the bike with the brake lines still attached and pumped the brakes to move the pistons out slightly. I did not pump them all the way out because I saw a guy on youtube pulling the pistons out easily using pliers over a bunch of rubber from old bicycle tire tube to avoid damaging the piston, but this proved to be difficult for me. To avoid damaging the pistons I tried to grab with very limited force (also using thick layer of rubber under pliers for protection) and when I failed I decided to just connect the brake lines and pump the pistons out as much as I can. Before that I pushed the pistons back in with clamps to get rid of the air. So I connected the brake lines to the calipers and went ahead with the bleed procedure, but the problem is - the brake lever stays completely soft and spongy even after I get brake fluid with no bubbles coming out of the bleed nipples on calipers. None of the pistons have moved at all from the full in position and lever is soft and can be fully pulled in with no pressure no matter how much I try to bleed.

Now I can't fogure out what to do next? Did I mess something up, or is it possible that something is broken? Could some air in the system cause the brake lever to be completely soft, while bleeding procedure pumps clear fluid with no bubbles at the bleed nipples?
 

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you have air in the master..and the MASTER needs to be bled prior to hooking it up to ANY lines headed down

id recomend tho that if your doing the fronts..you do the ENTIRE front that means rebuild the master as well...it wont cost you much extra...sound be around 15-20$ for the master kit....and its useualy the master that fails before the calipers....to bleed a master you need to basicly have a line comming out of it back into the resevoir and pump it slowly with the end of the line in the fluid of the master...pump till ZERO air comes out then connect up to the rest of the system....

however in my experiance ive run into problematic bleeding of fronts on MANY bikes where i had to get out my vac bleeder and vac pull air bubbles out of the master thru the hole at the bottom of the resevoir before i could get any bleedability out of them....in fact i wont touch the front of a bike without a vac bleeder.....can it be done without..sure..but you may find yourself cussing and screaming at it LOL

NO ONE will recomend it as it can be dangours but you CAN use compressed air to get pistons out..however have something to catch them they can come out like a cannonball..another option is a grease gun and forcing them out with grease pressure..it works too but leaves you a huge mess to clean up...ive been forced to do compressed air many times..
 

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Right, I will go out looking for master cylinder rebuild kit and try to bleed the bloody thing. I never knew that the trapped air can be so hard to get out of the system and the effect it can have. I thought that even with air in the system I should feel at least little resistance on the lever, but the brakes are literally dead with lever as soft as if there was no fluid at all... They make it look so easy in those youtube videos :ripped:

Regarding the pistons, I do not have compressed air. I hope I can just get those things out once I get most of the air out. God this problem is annoying
 

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also check the bleed nipples
I had 2 of mine suck air in though the threads when open to bleed.
new bleed nipples sorted it
 

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a lil teflon tape can do WORLDS of good on the bleed nipples....and also aid in the bleeding itself by allowing less air/fluid passed the threads

a lil air can go a LONG way..and air in the master will make the whole system dissabled
 

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So I bled the master cylinder even though it did not seem to help at first, eventually I managed to get some pressure in to the system. A lot of cuss words definitely helped :) but the key was to to let some bubbles out of the little hole in the master cylinder(I guess some air had risen from the lines to the top during the night) and pump the lever for like 20 minutes straight. Unfortunately I managed to only pull the pistons out from one side, since I mismanaged the process a bit and a piston popped out on one side, while the other side was still about 25-30% in the caliper. While inspecting the caliper from which I did manage to get the pistons out I came to conclusion that it probably had never been serviced. The seals were in terrible shape and there was a LOT of crud around them.

Now I will have to rebuild one of the calipers and go through the bleed process 2 more times. Once to get the remaining pistons finally out and then to put things together.

Before I put the new seals in I have a couple of questions:

1. The new inner calipers seals look a little bit smaller than the old ones. It looks to me that he old ones are just stretched out, but want to be sure...

2. Are the piston seals symmetrical for a ZR-7? I saw one video on youtube, where a guy was putting a lot of emphasis that you need to put the seals in with the correct side up. He was illustrating this with a story of a dude who did it the wrong way and then sued Ducati for not printing instructions on the box after he lost his brake fluid and almost killed himself. But with the seals I bought I just can't see any difference and they just seem symmetrical to me...
 

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seals on brake parts both stretch out and swell to a larger size...so ignore that

the "up" side is not refering to left/right but top/bottom of the seal itself..they useualy have a "flange" that you can slip your fingernail under....basicly..just make sure the NEW seals go on the same way the old ones were on there
 

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Finally got the pistons out, but it looks like I will need at least one of them replaced. Does anyone have informaton on what other bikes if any might have the same brake pistons as on ZR-7. Or is it that most every bike will have a different brake piston size?

Also how perfect brake piston should be so I can safely use it? I am sure it is recommended to change the piston if it is even slighly scratched, but a couple of mine were pretty dirty and a little bit damaged, but there was no leaks...
 

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post up pic's..youve gotta have some SERIOUS scoring before you cant use them..to be honest the piston just rides the bore..the seal and seal area are more important..so is the calilper which can be re-honed
 

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caliper.png

Here is the picture with the worst of it. I will probably just use these calipers for now. I am planning to change the brake lines pretty soon anyways, so I can swap pistons then. That will give me time to look for a better deal on them.
 

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in all my years ive used ALOT worse than that and never had an issue......the wheel cyls on my 58 ford are a good example of that..they make yours look pristine by comparision..i rebuild those units back in the 90s and they still work perfect with zero leakage..heck the mast cyl piston on my xl600r looks worse than that too and no issue
 

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OK so I put everything together, but surprisingly there seems to be a very tiny leak from the pistons somewehere. I did not see any leaks when the pistons started moving out under pressure, but when everything was put together there was a small drip of brake fluid on both sides and I whiped it off. After a short ride I could still detect a small amout of brake fluid but only on one side. Again surprisingly the side that is leaking is where the pistons were in a better shape. It does seems to me that the leak might be slowly decreasing. Could it be that the seals are slowly expanding and it will stop eventually?

Anyways even after bleeding the lever is spongy, but now I actually have a usable lever even though there still is a little bit of air hiding somewhere in the system. Is it possible to somehow get the last of the air out, without getting the calipers off again? Im just a bit tired of cleaning the brake fluid off my hands. What if I get that vacum tool thing and start pumping fluid through the bleed screws upwards, because I suspect that the air just doesnt want to go down and stays somewhere in the lines if I do the traditional simple bleeding procedure...
 

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a vac pump is a good tool..and what ive found best is a lil ...weird...you fill the bottle half full..and put the pencil tip on..stick it in the master and pull pressure out of the hole in the bottom of the master..

with a good bit of pressure pump the lever SLOW and them release the vac presure which will pump fluid back in..this "should" remove any air left in the line and the master..but you may have to repeat it a few times...if that fails to help then you have a air bubble in the callipers..and you need to start by re-bleading them...teflon tape the THREADS ONLY on the bleed nipples and then vac bleed them before the master...trying to vac bleed without taping the nipples youll get false readings as air goes past the threads

as for the leaky caliper..did you miss match any of the pistons..ie not in the same hole they came out of?....how was the bores in the callipers themselves?....the seals will work themselves in..but a leak with enuf fluid to drip worrys me...
 

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The pistons may have been mixed up, since I lost track of the order at one point. The bores were pretty dirty with a lot of hardened salt like dirt accumulated behind the old seals. I scrubbed it out and cleaned them as best as I could.
 
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