Factory rear brake rotor compatibility

Need some rear brake rotor compatibility help here. I've got a 76 KZ900 that I'd like to convert to a rear disk. Got about everything I need except the rotor itself and a master cylinder. This is what I'm using and it all bolts up fine so far.

77 KZ1000 A1 swingarm, rear wheel/hub
76 KZ1000LTD caliper, caliper brkt, and torque rod (I like this style caliper better)

I'd like the rear disk to match the newer factory asymmetrically drilled front rotors I'm using. I'd like the 2 peice style with the aluminum carrier with the rotor riveted to it instead of the one peice style KMM #41080-0008 used on the 77/78 KZ1000 A1/A2. It looks like KMM #41080-1020 for a 78 KZ650D2 might work. Anyone know if anything else has the correct OD and offest to work with this setup?

I think the 650CSR front brakes's had the approx 11" OD I need but the offset might be wrong. I don't have the correct rotor to measure to compare anyway. I might just order one of the one peice ones off ebay for now so I've got something. I have a 440LTD front rotor that is just under 11" it measures about 7/8" from the mounting surface to the outer disk surface which seems about right but the ceter hole is 2.5" instead of 2.25" and it would need the bolt holes redrilled and they would be right at the edge of the hole. I'd like to get a factory part that fits right if possible.

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Thanks for the reply. That is the type of rotor I'd like to use. I'll try and attach a pic of my caliper but I'm using an older style that they only used on the 76 900LTD and on the 750 twins as far as I know. I like that look for my build. I think that the rotors may be the same size though. I need one that is about 11" to fit. I'll have to keep an eye out for one like yours with the 8 rivets instead of 9. You don't happen to know what that originally came off do you? Going though the parts diagrams on Kawi's site it looked like everything that came with spoked wheels originally had the one peice rotors.

I got one and measured it. 10 7/8 inch.

These came on LTD.....I will try to get you a part number....I went though what you are going though now and really threw my for a loop untill I figured it out with help from this forum.

They are on Ebay all the time....they arent hard to get. I great condition....thats different.


www.cmsnl.com/kawasaki-1977-kz1000-b1-kz...t/61472.html#results

The Kawasaki Rotor Part Number: 41080-1020

Hey, thanks once again. I was thinking that the 41080-1020 would work. Still curious if the 650CSR or 305 CSR fronts might work on the back. They look similar with the 8 rivets. Maybe they are just thinner disks since they were duals on the front of the 650 and the 305 was such a small bike. Offset might be wrong though. I'm running 4.5mm min thickness dual setup on the front. That is what the 440 front I have is. Wish I had some bikes to measure. I'll see if I can get anyone on ebay to measure their parts they have listed.

I know I'm over thinking all of this but I guess that is part of the fun (or frustration) of it.