1980 Kawasaki KZ1000 B4 LTD .Rear Master Cylinder

Hi everyone,
I have been working for 2 years, on restoring a 1980 Kawasaki KZ1000 B4 LTD ,and am running into problems locating a compatible replacement Rear Master Cylinder

.The OEM rebuild kits are obsolete, and as far as I have searched, no one is offering an aftermarket rebuild kit for this make and model.
Here is the One Million Dollar Question..........
Has anyone come across a suitable replacement ,for the entire unit, with the least amount of modification work?

I was planning to restore this bike ,back to it's original condition, but am now finding out that Kawasaki is making this impossible for me, to do.
This is not the only bike of it's kind, and was hoping to connect with someone that has more insight.

I have learned a wealth of knowledge so far ,and am willing to share this with others , that have similar machines.
I also would like to thank the Moderator ,for having this valuable and wonderful site available for all

Best Regards Karl

There's a nos piston assy listed on eb. search = 43072-004. part number from partzilla.

Within the realm of possibility. There may be another piston assy not listed for the 1000-B4 that might work, but that's something you'd have to figure out. I know of one case: on a Z!R Fr br mc the K&L 32-8052 can be used in place of the oem 43020-1008. Another example that I think will work is maybe the 650B Fr piston on the 81 650-csr --- from my own comparisons they appear to be very similar.

For comparative purposes. not for the B4 Ltd rear brake.

Do you think ,if I swapped the master on the 1980 Kawasaki KZ1000 B4 LTD.... for a 1979 KZ1000 B3 Ltd Complete unit ,do you think it would fit ?
I will keep searching, and try to find a rebuild piston.Thanks for the comparison , it looks like it should do the job.
If all else fails i will try this unit

khschneider01@yahoo.ca wrote: Hi everyone,
I have been working for 2 years, on restoring a 1980 Kawasaki KZ1000 B4 LTD ,and am running into problems locating a compatible replacement Rear Master Cylinder

.The OEM rebuild kits are obsolete, and as far as I have searched, no one is offering an aftermarket rebuild kit for this make and model.
Here is the One Million Dollar Question..........
Has anyone come across a suitable replacement ,for the entire unit, with the least amount of modification work?

I was planning to restore this bike ,back to it's original condition, but am now finding out that Kawasaki is making this impossible for me, to do.
This is not the only bike of it's kind, and was hoping to connect with someone that has more insight.

I have learned a wealth of knowledge so far ,and am willing to share this with others , that have similar machines.
I also would like to thank the Moderator ,for having this valuable and wonderful site available for all

Best Regards Karl

RedLine Cycle sells rebuild parts. I just rebuilt mine on my 1978 1000 LTD and its the same as yours. After soaking in PB Blast for a long time I was able to get the piston out by shooting compressed air into it. I purchased all the parts needed from Jim at Redline Cycle. I purchased a 5/8 ball hone in 320 grit off flea bay. ran it in the bore using break fluid as lubrication. only a few strokes at slow RPM. just enough to break the shinny surface and give the new seals something to wear into. its been on the bike now almost 6 months and no leaks.

martin_csr wrote: There's a nos piston assy listed on eb. search = 43072-004. part number from partzilla.

Within the realm of possibility. There may be another piston assy not listed for the 1000-B4 that might work, but that's something you'd have to figure out. I know of one case: on a Z!R Fr br mc the K&L 32-8052 can be used in place of the oem 43020-1008. Another example that I think will work is maybe the 650B Fr piston on the 81 650-csr --- from my own comparisons they appear to be very similar.

For comparative purposes. not for the B4 Ltd rear brake.

Those pistons look like replacements for a front trapezoid MC. I just rebuilt that one on my '78 1000 LTD also.

khschneider01@yahoo.ca wrote: Do you think ,if I swapped the master on the 1980 Kawasaki KZ1000 B4 LTD.... for a 1979 KZ1000 B3 Ltd Complete unit ,do you think it would fit ?
I will keep searching, and try to find a rebuild piston.Thanks for the comparison , it looks like it should do the job.
If all else fails i will try this unit

I don't know ifhe B3 & B4 mcs are the same. You can compare the parts on partzilla or Kawasaki.com.

As mentioned, there's a nos piston listed on eb. ... eebbaayy.

Hi : Martin,..... As I read numerous articles throughout this web site,I found you to be quite knowledgeable and learned that you have helped many people. My sincere thanks for your help, Now for the good news!.... I found, and Ordered OEM#43020-1015 from Ebay, it's probably the one you saw, and only one, which is coming from the Netherlands . .What confuses me is the seller's description of the part, as : Kawasaki KZ400 Piston assy rear brake 1977 1981 43020-1015.....And even more confusing is that Partzilla has listed in their schematics, the same master cylinder as a 79 KZ1000 B3 LTD.
I have a 79 Kawasaki KZ1000 B3 Ltd and purchased it brand new, it has a different rear master cylinder than the 1980 KZ1000 B4 LTD
I'm currently restoring. I remember reading , somewhere, on this site that someone mentioned that these master cylinders were only produced a short while.....that probably explains why OEM parts are so hard to come by.

If anyone is searching for a part #43020-1015 , I have located a place in Canada , that stock these in: ''aftermarket made in Japan''.


Hope this helps someone in their journey
Best Regards

Hi; Mikaw,
Make sure you change the ''O'' as well, below your reservoir ,( trapezoid front master cylinder)....
You know the one I mean?...the part that Kawasaki totally forgot about .
I had to buy a bag of 100, in order to get the job done. ,and glad I did!
Thanks for your input and thoughts in the previous messages

Best Regards

khschneider01@yahoo.ca wrote: .....
If anyone is searching for a part #43020-1015 , I have located a place in Canada , that stock these in: ''aftermarket made in Japan''.


Hope this helps someone in their journey
Best Regards

Hi, I need this item...can you help me?
thank you!