Front Mater Cylinder Issue KZ000 Z1R

Hey Folks, I have a front master cylinder on my 1978 KZ1000 Z1R that is no longer pushing fluid through the lines. I assume the rubber gaskets on the piston assembly are leaking. The original piston assembly has been discontinued. I found one promising replacement. It looks like the right part and is the right size (5/8"), but the part numbers don't match. I ordered it anyways and will give it a try but if it doesn't work. . .does anyone have any ideas how I may be able to get my bike back on the road?

SR2JR wrote:

Hey Folks, I have a front master cylinder on my 1978 KZ1000 Z1R that is no longer pushing fluid through the lines. I assume the rubber gaskets on the piston assembly are leaking. The original piston assembly has been discontinued. I found one promising replacement. It looks like the right part and is the right size (5/8"), but the part numbers don't match. I ordered it anyways and will give it a try but if it doesn't work. . .does anyone have any ideas how I may be able to get my bike back on the road?

Fingers crossed for possibily an easier fix and hoping that perhaps the existing m/c may be refurbished, so forgive some guesswork here.

Failure to push fluid at caliper bleed could result from air in the line curable by bleeding the system -- but of course you already know that -- so am assuming failure to push fluid from the m/c itself at the banjo joint. But even a leaking primary cup should push some fluid, whereas a missing primary cup would not push any fluid.

If cups are failing to seal, am guessing fluid would be leaking past the secondary cup and on to the outside (being visibly messy). If fluid is staying contained inside the m/c without leaking to the outside, the cups may be okay. An extremely pitted bore (unlikely IMO) could also result in leakage to the outside.

Could it be that either or both the relief port and/or supply port at bottom of the reservoir are clogged and thereby preventing fluid exchange between the reservoir and the bore?

If not already done, would suggest complete disassembly of m/c and a meticulous thorough cleaning, being extra-careful not to damage the existing cups. Use lots of rubbing alcohol, fresh clean brake fluid, and air pressure. Minor bore pitting may be buffed out a little. To assure it's pumping fluid, the m/c may be filled and bench-tested before reassembly onto the bike.

Has a part number cross reference via Kawasaki.com been done?

Here's hoping!

Thanks for the reply. Yeah I cross-referenced the part numbers and even sat for a couple of weeks before the dealership I originally ordered from told me the part was discontinued. I previously took the entire assembly apart and noticed no areas where the system could be leaking or clogged. I then tested just the master cylinder with the resevoir attached and noticed that when I activated the piston by hand it was only moving fluid from the resivor through the cylinder a couple drops at a time. I know fluid shouldn't come gushing out everytime I press on the piston but what kind of flow should I be looking for? And thanks again for your reply.

SR2JR wrote:

... activated the piston by hand it was only moving fluid from the resivor through the cylinder a couple drops at a time. I know fluid shouldn't come gushing out everytime I press on the piston but what kind of flow should I be looking for?....

Should be more than a few drops.

If fluid is freely moving from the reservoir supply port (the larger hole at bottom of reservoir) it should fill the bore area when the piston is in relaxed position, including the bore area between the primary cup and exit channel at the banjo.

If the area of the bore is full of fluid between the relaxed piston primary cup and banjo, squeezing the brake lever should push considerable fluid out of the m/c. For example, consider when bleeding brakes, the substantial amount of fluid passing out of the bleeder screw with just one squeeze of the lever.

Something is wrong, but I'm suspicious of the cause, and still not yet willing to blame it all on leaking cups, especially if there's no visible leakage of fluid escaping the m/c.

With the m/c relaxed, on the bench, with the banjo hole pointing upward, fill the m/c with brake fluid through the banjo hole. Now, squeeze the piston through its compression stroke. What happens? Does this maneuver push more that a few drops out of the banjo end?

And I could be wrong about this aspect, but is the m/c leaking any fluid out the lever (non-banjo) end?

It seems to me that if there's fluid filling the bore area between the relaxed primary cup, and you have any primary cup action left at all, compression of the piston must send the fluid somewhere, either out the banjo hole or to the outside (visible leakage) on the other end.

Or maybe I'm just totally missing something. But remain suspicious of the port openings at bottom of the reservoir, and yet have no reason to doubt your assurance they're clear and open.

Don't know history of the bike. Did the m/c suddenly fail while in regular use? Was it okay, then stored, and failed when put back into service?

Might be a lost cause after all, but am not yet willing to give up on your existing m/c.

Hope the replacement piston and new cups fit okay and cure the problem.

But if they fit okay, and still only push a few drops of fluid, it's really gonna piss you off. :laugh:

Well I gave it another shot and checked everything again. I checked for any clogs in the master cylinder itself and found none. I then reattached the resevoir and placed the piston back into the cylinder. I filled the resevoir and marked off the fill line just to see if the fluid went down at all. I then spent about ten minutes pressing and releasing the piston and only go drops again. There were no leaks from the piston end. I then took the resevoir off and just filled the top with fluid (not sure what the section is called but it contains two holes -one large the other smaller than a needle- and you connect the resevoir here). Again I compressed the piston and did not see the fluid drawn into the cylinder. I did get a couple of airbubbles though?! Once it was fully taken apart again I rechecked for clogs, and even used a bright light to shine through the holes(ports) I mentioned and I could see the light clearly on the inside of the cylinder.
And yes the brakes were working very well. Then the bike sat for about a month and when I went to move it in the garage and noticed that I had no front brake pressure at all. Bleeding the breaks didn't help. Just glad this happened while in the garage and not while doing 80 on the highway!!

SR2JR wrote:

Well I gave it another shot and checked everything again. I checked for any clogs in the master cylinder itself and found none. I then reattached the resevoir and placed the piston back into the cylinder. I filled the resevoir and marked off the fill line just to see if the fluid went down at all. I then spent about ten minutes pressing and releasing the piston and only go drops again. There were no leaks from the piston end. I then took the resevoir off and just filled the top with fluid (not sure what the section is called but it contains two holes -one large the other smaller than a needle- and you connect the resevoir here). Again I compressed the piston and did not see the fluid drawn into the cylinder. I did get a couple of airbubbles though?! Once it was fully taken apart again I rechecked for clogs, and even used a bright light to shine through the holes(ports) I mentioned and I could see the light clearly on the inside of the cylinder.
And yes the brakes were working very well. Then the bike sat for about a month and when I went to move it in the garage and noticed that I had no front brake pressure at all. Bleeding the breaks didn't help. Just glad this happened while in the garage and not while doing 80 on the highway!!

Thanks for the report.

Although inconsequential, I have mistakenly referred to the supply port and relief port as being located at bottom of the reservoir, because the Z1R remote m/c has a "pipe" connecting the reservoir to the ports whereby fluid moves in and out of the piston bore area.

Forgive me for wondering if reassembly might be incorrect, and for some rambling, but in review ---

You are certain that brake fluid from the reservoir is freely flowing from the reservoir through the "pipe" and plentifully supplied through the grommet into the m/c. Am wanting to assure ample fluid supply continuously available to the ports, that the pipeline is not clogged, and that there is no obstruction of flow between reservoir and m/c ports.

Could be mistaken but am thinking the primary cup is a separate unit and the secondary cup is already built in as part of the piston.

When reassembling the various parts into the bore, first the spring goes in -- big end first. Next the primary cup goes in the hard way (larger open side against the small end of the spring), then the piston (with built-in secondary cup), then the stopper, dust seal, and finally the liner (plastic retainer). At this point, you have yet to attach the lever and connect to the pipe from the reservoir.

Assure the spring is not in backwards.

Assure the primary cup is not in backwards. Larger open end goes in first with the smaller flat backside facing the piston.

Assure the primary cup is not turned sideways after insertion. And doesn't get turned sideways when inserting the piston.

Attach lever. Connect m/c to pipe and reservoir. Fill reservoir and wait awhile to allow the fluid to flow down into the bore.

With m/c in relaxed position, brake fluid should gravity-flow from the reservoir, through the pipe, through the ports (filling the spring area and the area around the piston between the cups), and fluid should keep gravity flowing on out through the banjo holes. This is why the banjo bolts must be tight or fluid will leak out with the bike just sitting there parked and without any brake pressure being applied.

If the primary cup is properly inserted, and is in the relaxed position with fluid filling the spring area between the primary cup and banjo holes, pushing the piston moves the primary cup past the tiny relief port at which time the fluid in the spring area has nowhere else to go but out through the banjo holes. And meanwhile, fluid gravity flows through the larger supply port into the area around the piston between the cups.

From a visual inspection, does the primary cup look all right, or is it obviously torn up?

Does the piston have a non-return valve at the primary cup end? If so, it should allow fluid to move during the release stroke from the area between the cups and around the primary cup into the spring area, which gives the primary cup a fresh supply of fluid to push out the banjo holes.

There may simply be a lot of air inside the piston area. When fully reassembled onto the bike, with lines connected to the calipers, might consider back-filling with fluid from the caliper bleeder valves so the fresh fluid can push air from the system as the fluid passes backwards through the banjos into the m/c bore and on up through the ports and then through the pipe and gradually fill the reservoir. The reservoir top should be removed during this procedure (and when bleeding). When doing this, I use a bulb syringe with short length of clear plastic tube between it and the bleeder valve. Suck plenty of clean fresh fluid into the bulb syringe and squeeze the bulb to remove air before injecting fluid into the bleeder valve. Take your time - go slowly, and with just a little pressure on the bulb.

You will still have to finish bleeding the old fashion way, but hopefully then dealing with much less unwanted air inside the lines, and m/c, and reservoir.

Here's a pic for reference.



Don't give up. Still hoping your existing m/c will be okay.

Post edited by: Patton, at: 2007/09/21 20:05

And yes the brakes were working very well. Then the bike sat for about a month and when I went to move it in the garage and noticed that I had no front brake pressure at all. Bleeding the breaks didn't help.

Was level of fluid in reservoir checked before bleeding was attempted?

Was additional fluid added to an "empty" reservoir?

Perhaps the initial bleeding operation was simply insufficient. Some of these brake systems are extremely difficult to properly bleed. And especially when beginning with a dry system.

And yes the brakes were working very well. Then the bike sat for about a month and when I went to move it in the garage and noticed that I had no front brake pressure at all. Bleeding the breaks didn't help.

To me it seems most improbable that "working very well" m/c piston, cups, and/or bore condition could ruinously deteriorate after only a month or so sitting in the garage.

Upon disassembly, was the m/c found to be in super-nasty condition? (And even that is far from hopeless).

Just another reason for believing your existing m/c may still be okay.

Post edited by: Patton, at: 2007/09/21 20:43

Thanks for the info. The new piston (which hopefully will fit) should arrive today so I will follow your advice and see if I can't get this thing to work. Now that I think about it; when I did notice that I had no front brakes, I did check the resevoir and founf it empty. This prompted a search for a leak but found no evidence. I then tried bleeding the brakes but probably didn't put in enough time. I did check the cups and I noticed that one of them is a little worn around the edges. I did have to clean a good amount of gunk form the cylinder when I first took it apart and the old dust cover and a couple of holes in it. Hopefully the new part will arrive today and I can try this again with a different piston! If I can I'll put a picture of the old piston online.

note

Tried to upload a diagram with notes but it hasn't worked. I'll give it a shot again later.

Post edited by: SR2JR, at: 2007/09/24 12:12

Post edited by: SR2JR, at: 2007/09/24 12:14