Z1R Front Master Cylinder Rebuild Kit Substitute

I've been looking for a substitute piston and seals for the Z1-R front master cylinder for a long time, but I have never seen anyone suggest an alternative.

So I did my own research, and I wanted to post it here for anyone who needs it.

The discontinued factory master cylinder piston assembly for the 1978 and 1980 KZ1000-D1,D3 Z1R is part # 43020-1008. That's for searching.

I found an NOS Kawasaki part from a guy in Greece, of all places. Once I had that, I compared it to a standard KZ1000 dual disk master cylinder rebuild kit. I bought the K&L kit, part number 32-8052.

In all ways that are important, the dimensions are identical. I measured everything I could, using a micrometer and caliper, but the most important in my opinion is the distance from the back of the first ring (which sets the resting position) to the front of the two seals, and the distance from this same surface to the tip of the pusher end. I also measured the spring wire diameter and free length. Nearly every feature measured within a few thousandths of an inch of each other. Many are within 0.001".

The one area where where there is a noticeable difference is the diameter of the metal rings behind the seals. The OEM measured 0.624, and the K&L measured 0.619. The rubber seal diameters are identical, at least as close as I can measure them since they are soft. I figure the seals are what actually contacts the cylinder bore, so the 5 thousandths missing from the piston diameter doesn't seem like an issue.

Also, I believe the OEM piston is all steel, while the K&L is maybe aluminum, with a steel cap on the pusher end.

After all of this, it seemed safe to go with it. The K&L part has been in my bike now for almost 1000 miles, and it works perfectly. The brakes are just as wooden feeling as they were before.

So there you go. What was once impossible is now easy. Buy the kit from Z1 Enterprises, because they are a fantastic outfit:

www.z1enterprises.com/ListItems.aspx?keywords=KL32-8052

If anyone wants more specific details on the differences between the two, ask. But it's pretty clear that the Z1-R master cylinder, while very odd externally, used all the same internal dimensions as the standard handlebar mounted master cylinder. So any kit, OEM or aftermarket, intended for the standard bikes (with the 5/8" cylinder) is likely to work with the Z1-R.

Here are links to pictures, since I can't figure out how to embed them in this post.
] picasaweb.google.com/lh/photo/F-mftbVKMu...lgIg?feat=directlink

] picasaweb.google.com/lh/photo/GNwSUUtNcF...lgIg?feat=directlink

thanks for that info dohc.
i captured and inluded your pics.






as someone who owns four z1r's i am all too familiar with the wows of the front brake master cylinder.
i have two m/c's that are frozen up.
i had been wondering about trying to get them apart and rebuilt,but had been somewhat worried because of the horror stories of finding rebuild parts.

thanks for doing the legwork and posting the info for the rest of us to benefit from.

now :whistle: ,
how bout some pics of the z1r that the rebuilt master cylinder is on for our viewing pleasure :evil: .

leon

Ya....

ive noticed on the re-poped plungers / stuff that this collar is different on most if not all kits.

I think this is related to the method for allowing fluid to flow around the front seal (back to front) on the return stroke. The OEM unit has holes drilled through the ring behind the front seal, with a thin metal disk just behind the front seal to cover these holes when there is pressure on the seal face, basically a check valve. The K&L doesn't have any of this, expect some flutes molded into the back of the seal. I assume they just figure the fluid will pass around the front ring, and cut that cone into it to help it pass more easily?

I can say that I didn't have any issue with getting the system to pump up when I first installed it, so the fluid appears to pass around the front seal on the return stroke just fine.

Can the plastic tip and spring on the end of old plunger be transferred over to the new one?

Not really. The plastic ring snaps onto a small post at the nose of the piston. There is no equivalent post on the K&L unit.

other items such as plastic dust boot sleeve and half moon washer ... will need to be reconditioned and used again as kit doesn't include them

I'm not sure which kit you were referring to, but the K&L kit does include the dust boot and the "C" washer, which also fit the Z1-R. But Kawasaki shows that these parts were shared with many other models, so I was confident that those would work fine.

And just to complete the part number references, the dust boot is part number 49016-1010, and is still an active part.

How is this working out after 4+ months of use? Those Z1R front m/c kits have been a pain - so if this kit is useable, that's great news.

Similarly on the 80 rear master cylinder, the piston is very unique, but this same master cylinder kit can provide the seals to refurbish the old piston - you just have to transplant them.

Jeff.Saunders wrote: How is this working out after 4+ months of use?

Hey Jeff,
It's working perfectly. I haven't removed the fairing recently to confirm that there are no leaks, but so far the operation is flawless. When I first installed it there was a slight pop/catch at the very beginning of travel, but that went away pretty quickly.

The item I need now is the front reservoir rubber diaphragm (43028-1003). Mine has a tear and is letting moisture in. The fluid is pretty dark already. Have you heard of anyone making a reproduction part for this?

I'm not aware of any aftermarket part. I rechecked dealer stock and didn't find any of those in the USA - at least with dealers who list their old inventory in the NOS service we belong to.

I'm in the same boat. The front reservoir rubber diaphragm (43028-1003)on my Z1R has morphed into a 2.5inch black leaking caterpillar. Any ideas anyone?

No eBay APP ID and/or Cert ID defined in Kunena configuration

bluflame wrote: I'm in the same boat. The front reservoir rubber diaphragm (43028-1003)on my Z1R has morphed into a 2.5inch black leaking caterpillar. Any ideas anyone?

My plan is to replace the stock reservoir with one from a modern bike. I searched through a ton of ebay listing and decided that the rear reservoir from an 06/07 GSXR600/750 looked the most promising.



The output exits in basically the right direction and the mounting surface is on the correct side. It even looks like the tube that comes with it has the 90 degree bend that would be needed to feed it over to the master cylinder. These are also still available new from Suzuki.

The main drawback I see is that it's way smaller than the stock unit. I figure as long as I keep an eye on it and don't let it get low it shouldn't be a issue.

I have one on my bench, but I haven't had time to actually try to fit it. If anyone else makes it work, please share pictures.

Here is the auction that I stole the photo above from:

Was out of stock at Z1, but vendor on Amazon had one. Ordered it up for my old girl. Thanks!

out in the shop last weekend and went to move the 80 z1r,and the front brake lever went all the way to the bar :sick: .

looks like it is time to give z1e a call and get that kit ordered.

thanks again for the info dohc.

leon

thanks again for the info dohc

I'm happy to help. I can't even tell you how many hours I've spent learning about the odd little details of the Z1-R. It's nice to feel like there was some point to all that.