are they interchangable discs ?

Z1KZonly....so do you mean that I can only use the front rotors ??...what would I have to do for the rear ?...would I have to replace the caliper, with a Z1R one ? or the swingarm

No, you will be fine.
I meant use the 2 front on front.
And the rear on the rear.
Front and back have same bolt pattern but a little different offset.
Can't mix frt & Rear
From what I remember using a disc on a CCR Dragwheel 20 years ago.

When you get them Snap-On Tool guy has a nice surface flap wheel for an air tool.
Looks like you just surfaced the disc, if you want to clean them up.

THANKS...for all your know how !! my stepson has one of those flap wheels, I"ll definetly have to do that, your rotors look like new, I"ll have to do my old ones before I put them on e-bay....Thanks again...Pete.

z1only just started to replace the rear disc & when i put them back to back the Z1R disc is about a 1/4 inch bigger than my LTD disc,,......do I need to have a Z1R brake caliper ?????

You will get more stopping power out of the later discs than out of the Z1R discs. The newer discs are much more efficient.

pete greek1 wrote: ...just started to replace the rear disc & when i put them back to back the Z1R disc is about a 1/4 inch bigger than my LTD disc,,......do I need to have a Z1R brake caliper ?????

FSM says 250mm disc diameter front and rear on 1978 Z1R (KZ1000-D1) and 1979 Z1R-II (KZ1000-D2).

Don't know what diameter FSM specifies for 1980 KZ1000-B4 LTD.

kawasaki.com doesn't help very much, because the different hole patterns will carry different part numbers even on otherwise identical parts.

If both rotors are exactly the same (offset and thickness) except for 1/4" larger diameter, the larger rotor's circumference will run 1/8" closer to the stock caliper.
I don't know from actual experience whether that would allow sufficient clearance between the rotor and caliper.
However, given sufficient clearance for the rotor to spin within the caliper, with 1/8" less clearance than stock, am thinking the larger rotor would function okay in the stock caliper.

But that's armchair engineering at its worst.

I would fit the larger rotor with the stock caliper, and hand-spin the wheel while observing clearance between the rotor's edge and the caliper.

Good Fortune!

Sorry to say but the Z1R disc's were about 1/4 inch bigger in circumference than the LTD 1000 disc's. They will not fit with the LTD 1000 calaper, the rear Z1R disc's were stamped 2S and the LTD 1000 disc's were stamped 4V. They are about 1/8 to 1/4 inch short of clearing the disc.

Thanks for all your help for trying to find out if my disc's were innerchangable. After trying to assemble them, they were still about 1/8 to 1/4 inch to big. Now I am worried about the front disc's fitting. My front disc's on my LTD 1000 are marked 4T and the Z1R disc's that I purchased are marked 2L. I would appreciate if you could look up to see if I am going to need 2 front calipers also, because it looks like I am going to need a new Z1R caliper for the rear.
p.s. Can you see if I am going to need 2 front Z1R calipers?
Thanks
Pete

If you install the matching calipers than they will fit. Or go with the leading axle caliper bracket.

will i have to replace all 3 calipers to Z1R ones? or just the rear caliper ? ....I havent gottn to the front ones yet,.....P.S. what do you mean about going to the leading axel caliper bracket??

will I have to replace all 3 calipers? or just the rear one with the Z1R caliper? & will the 78 Z1r calipers mount right up tothe forks on my 80 LTD..... P.S. what do you mean about goig to the leading axel caliper bracket ?