Kawasaki Motorcycle Forums banner

1 - 19 of 19 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
If anyone could give me any advise, that would be great.
I found rust and pit on pistons of front left and right brake clippers during cleaning. I replaced pistons, piston seals and dust seals. I thought that it is time for refresh. So, I replaced master cylinder piston and seals also.
Since then, brake is spongy. I bled many times to air out. Any size of bubbles don't come out anymore form calipers, ANDFs, joints and master cylinder port.
Pistons move out from beginning of squeezing lever. Lever play (0 to where the point of a lever feed back becomes harder) is about 1 inch. I hear slight squeaky noise from the master when I pulled lever. (It didn't happen before master refresh.)
Is air still in somewhere? Is caliper piston seals taper and I placed in wrong? Shoud I replace original hose to new?
Thank you,
 

·
Registered
Joined
·
770 Posts
If you are not having any leak, try leaving the reservoir cap loose, and leave pressure on the lever overnight by using a strong rubber band or small bungee. It will feel better in the morning, but in general, once you open the system to air, it is very difficult to get it as hard as factory. It is like a microscopic air bubble remains in some crevice and is hard to take out. I suspect they pressure fill the system at the factory, and it makes sense because takes too long to fill manually on a fast moving assemble line.

It is also possible to fill in reverse with a syringe from the caliper bleeder. The theory is the air likes to go up, not down, but even this may not get it as before.
 

·
Registered
Joined
·
4,493 Posts
If the motorcycle has the original rubber brake lines, I would replace them w ss braided lines. There are all sorts of choices, but I went with Goodridge from Z1Enterprises dot com. CycleBrakes dot com has Galfer lines which have crimped-on fittings. As for bleeding them, I installed a speed bleeder which makes the job much easier. Something else I do is elevate the caliper with the bleeder oriented upwards & shim the brake pads very tight. One time I happened to have a dishwasher box in the garage which came in handy for elevating the caliper. hee.
 

·
Registered
1983 GPz 750, green
Joined
·
38 Posts
Hey ZX-KZ, one thing I have found with my 750's is that sometimes air gets trapped at the reservoir. By tilting the reservoir and pumping the lever the air gets released into the reservoir. They are supposed to be flat but then the air gets trapped. Also you could try hooking up a vacuum to the bleed screw and sucking the fluid through. Both have worked for me.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #5
If you are not having any leak, try leaving the reservoir cap loose, and leave pressure on the lever overnight by using a strong rubber band or small bungee. It will feel better in the morning, but in general, once you open the system to air, it is very difficult to get it as hard as factory. It is like a microscopic air bubble remains in some crevice and is hard to take out. I suspect they pressure fill the system at the factory, and it makes sense because takes too long to fill manually on a fast moving assemble line.

It is also possible to fill in reverse with a syringe from the caliper bleeder. The theory is the air likes to go up, not down, but even this may not get it as before.
Thank you for your response.
I hear / read bungee method from YouTube, any forum, and even motorcycle shop. So, I have tried the bungee. It made lever feel better. However, it became back to too much play again after few squeeze. This method doesn't seem permanent solution... How did it happen when you tried it? It didn't work on me because there is very subtle leak which is not noticable from visual inspectionor any other issues?
I didn't loose cap. I will try loosing cap.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #6
If the motorcycle has the original rubber brake lines, I would replace them w ss braided lines. There are all sorts of choices, but I went with Goodridge from Z1Enterprises dot com. CycleBrakes dot com has Galfer lines which have crimped-on fittings. As for bleeding them, I installed a speed bleeder which makes the job much easier. Something else I do is elevate the caliper with the bleeder oriented upwards & shim the brake pads very tight. One time I happened to have a dishwasher box in the garage which came in handy for elevating the caliper. hee.
I have removed calipers from front fork and hang them slightly higher than the master cylinder for one night. Then, put them back to the fork and bled manually. Another time was bled with Mityvac. It didn't change anything. I tried it because a shop who used to take care of my GPz told to me. They did very good job every time. They made play 0 always. I should have ask more details...
Can you tell me more details what you do? How high elevete the caliper? Do you bleed before you do it? Do you bleed after that also?
 

·
Registered
Joined
·
11 Posts
Discussion Starter #7
Hey ZX-KZ, one thing I have found with my 750's is that sometimes air gets trapped at the reservoir. By tilting the reservoir and pumping the lever the air gets released into the reservoir. They are supposed to be flat but then the air gets trapped. Also you could try hooking up a vacuum to the bleed screw and sucking the fluid through. Both have worked for me.
Hey, Alex GPz,
I see. So, remove master/reservoir from handle bar. Tilting it and ump the lever at same time, right? Let me try it.

A vacuum you are mentioning. Is it the one hook up to a compressor? I have a Mityvac. It seems that the vacuum force is not strong. or I am I using it incorrectly? How I use it is that building pressure to 15 to 20 psi, open a bleeder 1/4 turn, shut bleeder before pressure goes to 5 psi or keep pumping to keep pressure. Of course I shut a bleeder before the reservoir empty.
 

·
Registered
1983 GPz 750, green
Joined
·
38 Posts
I'll try to describe better; What I noticed with my bikes after re-doing the brake fluid is this: air seems to get trapped right where the brake hose/line leaves the reservoir (the banjo joint), by tilting the reservoir the air is allowed into the reservoir and bubbles up. Do it a few times and pump the lever, then wait a bit for more air to escape keep it tilted. I use a home made vacuum pump with a collection jar (kinda like a hospital vacuum system). Connect it to the bleeder screw and start sucking fluid through, but keep pouring new brake fluid into the reservoir, don't let it go dry or you'll get more air. If your jar is clean you can re-use the brake fluid. Hope that helps you.
Sometimes air doesn't rise but can be sucked through, espeacially the tiny bubbles.
 

·
Registered
Joined
·
673 Posts
If you pull the brake lever hard and hold it, what happens? Does it stay there or does the lever slowly move towards handlebar? Hold it for like a minute or two to see if there is any motion at all.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #10
If you pull the brake lever hard and hold it, what happens? Does it stay there or does the lever slowly move towards handlebar? Hold it for like a minute or two to see if there is any motion at all.
I pulled the lever and held for a minute. I tryed to keep holding it with same amount of pulling force.
I think that I felt lever trying to move back or becoming harder. It is hard to tell because I felt my finger is exhausting. So, it could be stay there.
I think that the lever didn't move towards handlebar unless I increase pulling force.
 

·
Registered
Joined
·
673 Posts
Ok that's good. I was trying to rule out a master cylinder seal that may have gotten damaged during install or was installed backwards. I think we can rule that out.

So the spongy feel can really only come from air or because the rubber lines are old and weak and are swelling with pressure. But this should not suddenly occur just because you worked on your brakes. Although if a hose got kinked or strained during your repairs then maybe it has been weakened enough to swell giving you a spongy feel. I would put that into a low probability category for now.

I recently changed my brake fluid and was surprised to also have a spongy feel when I was done. My fix was to train the wife to operate the brake lever and keep an eye on the level in the reservoir while I manually bled the brakes. This allowed for a very rapid, smooth process and it worked for me. Perhaps by keeping the fluid moving, the air bubbles don't have time to return to their high point where they love to hide.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #12
I'll try to describe better; What I noticed with my bikes after re-doing the brake fluid is this: air seems to get trapped right where the brake hose/line leaves the reservoir (the banjo joint), by tilting the reservoir the air is allowed into the reservoir and bubbles up. Do it a few times and pump the lever, then wait a bit for more air to escape keep it tilted. I use a home made vacuum pump with a collection jar (kinda like a hospital vacuum system). Connect it to the bleeder screw and start sucking fluid through, but keep pouring new brake fluid into the reservoir, don't let it go dry or you'll get more air. If your jar is clean you can re-use the brake fluid. Hope that helps you.
Sometimes air doesn't rise but can be sucked through, espeacially the tiny bubbles.
I finally could have a chance to try it last evening.
I tiled the master/reservoir, (lever side up and banjo down), wait a while, pump lever gently. I also tapped banjo, bottom of reservoir bottom with screwdriver handle at second tilting.
I didn't improve anything...
 

·
Registered
Joined
·
11 Posts
Discussion Starter #13
Ok that's good. I was trying to rule out a master cylinder seal that may have gotten damaged during install or was installed backwards. I think we can rule that out.

So the spongy feel can really only come from air or because the rubber lines are old and weak and are swelling with pressure. But this should not suddenly occur just because you worked on your brakes. Although if a hose got kinked or strained during your repairs then maybe it has been weakened enough to swell giving you a spongy feel. I would put that into a low probability category for now.

I recently changed my brake fluid and was surprised to also have a spongy feel when I was done. My fix was to train the wife to operate the brake lever and keep an eye on the level in the reservoir while I manually bled the brakes. This allowed for a very rapid, smooth process and it worked for me. Perhaps by keeping the fluid moving, the air bubbles don't have time to return to their high point where they love to hide.
When you bleed manually what do you do?
I do
  1. Squeeze lever 2 times to build up pressure
  2. Hold lever as hard as possible at the third squeeze
  3. Open bleeder between 1/4 to 1/2 turn and shut quickly
  4. Add fluid before hole exposed. Probably add fluid level 3 mm above the hole.
The order is from left caliper, right caliper ,left ANDF, right ANDF, left junction, and right junction.
Order of caliper, ANDF and junction is according to the service manual.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #14
I'll try to describe better; What I noticed with my bikes after re-doing the brake fluid is this: air seems to get trapped right where the brake hose/line leaves the reservoir (the banjo joint), by tilting the reservoir the air is allowed into the reservoir and bubbles up. Do it a few times and pump the lever, then wait a bit for more air to escape keep it tilted. I use a home made vacuum pump with a collection jar (kinda like a hospital vacuum system). Connect it to the bleeder screw and start sucking fluid through, but keep pouring new brake fluid into the reservoir, don't let it go dry or you'll get more air. If your jar is clean you can re-use the brake fluid. Hope that helps you.
Sometimes air doesn't rise but can be sucked through, espeacially the tiny bubbles.
When you bleed your 750, which do you bleed first? When I do, order is from left caliper, right caliper ,left ANDF, right ANDF, left junction, and right junction.
 

·
Registered
Joined
·
673 Posts
The procedure I use for manual bleeding is pretty much the same but I made some edits for clarity so we are on the same page:

  1. Squeeze lever 2-3 times to build up pressure
  2. Hold lever firmly at the third squeeze
  3. Open bleeder between 1/4 to 1/2 turn and after lever is touching handlebar shut quickly and then release brake lever.
  4. Add fluid before hole exposed. Add as much fluid level as the reservoir can safely hold. You can always bleed any excess out or syringe it out when you are done bleeding.
Note: Use only brand new brake fluid that is rated for your motorcycle.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #16
The procedure I use for manual bleeding is pretty much the same but I made some edits for clarity so we are on the same page:

  1. Squeeze lever 2-3 times to build up pressure
  2. Hold lever firmly at the third squeeze
  3. Open bleeder between 1/4 to 1/2 turn and after lever is touching handlebar shut quickly and then release brake lever.
  4. Add fluid before hole exposed. Add as much fluid level as the reservoir can safely hold. You can always bleed any excess out or syringe it out when you are done bleeding.
Note: Use only brand new brake fluid that is rated for your motorcycle.
Thank you for edits. Yes, I use only new Kawasaki fluid and I don't reuse fluid once it came out from bleeder.
I begin bleeding from the farthest caliper from the master. I don't see any bubbles come out at all even I keep bleeding until the timing I refill the reservoir. So, I bleed another bleeder. And again. No bubbles. Maybe I am switching too early?
How long or how much of fluid do you bleed per one location?
 

·
Registered
Joined
·
673 Posts
You bleed until you see new, clean fluid coming through. It varies from bike to bike but I would think about 3 to 4 reservoir top-ups would do it. So, from nearly empty to full 3-4 times. Obviously the 2nd caliper will not need nearly as much fluid. You should completely finish with the first caliper before you move to the next. If your caliper has dual pistons with two bleed screws you will have to bleed both bleed screws.

Yes starting with the furthest caliper is best.
 

·
Registered
Joined
·
9 Posts
If the motorcycle has the original rubber brake lines, I would replace them w ss braided lines. There are all sorts of choices, but I went with Goodridge from Z1Enterprises dot com. CycleBrakes dot com has Galfer lines which have crimped-on fittings. As for bleeding them, I installed a speed bleeder which makes the job much easier. Something else I do is elevate the caliper with the bleeder oriented upwards & shim the brake pads very tight. One time I happened to have a dishwasher box in the garage which came in handy for elevating the caliper. hee.
put a hose on the bleeder run it up a foot straight up then turn and down into a can. open bleeder.let fluid run out or pump lever. keep fluid it dont run out. watch the. air come out. it works it's way up the hose . when air stops tighten bleeder. u good to go.
 

·
Registered
Joined
·
42 Posts
Air gets trapped in the corners where the banjo bolts are screwed into the Master Cylinder, Caliper, and Splitter (if the bike has one)'. It helps tremendously to 'bolt bleed' at each banjo bolt using the same process used at the Caliper bleeder screw but the banjo bolt is loosened until fluid (and bubbles) starts coming out the joint(s). It can be messy but it's effective.
 
1 - 19 of 19 Posts
Top