First post Front Brake Rotor Sizing

Hi there, not sure if this is the right place to ask.

I’m looking for a front brake rotor for my bike.

It’s a 1984 KZ750 twin I replaced the front end with a 82 KZ750 twin csr.

Front callipers and rotors match each other but when I took it to get a safety inspection they found a tiny crack in the front rotor.

The rotor is 130mm ID and 280mm OD.
Looks identical to all other Kz rotors of the time but online I can only find 260mm OD or 270 OD rotors.

Does anyone know what this rotor could be off of?
 I need to buy a replacement but EBay doesn’t seem to commonly list diameter just rotor thickness.

The 279 one will be correct if it's the same offset and bolt mount.

My bad that was supposed to be 270mm rotor that I found. I still haven't found this 280mm rotor.

There was a typo in my original question I've since edited. I could only find a 260mm rotor and 270mm rotor. I still need to find the 280mm rotor which would match what I have now.

Sorry I had a typo in my original message that I've since corrected. I need a rotor that has an OD of 280mm and i have only been able to find ones that are 260 and 270mm.

 I replaced the front end with a 82 KZ750 twin csr....  Does anyone know what this rotor could be off of?

a pic would help. it's probably the 750csr disk. could be unique to the model. you'll need to verify but the 650csr and 1000csr may have had similar disks that are different than the 70s models. my original 1981 650csr disk measures 281mm (11-1/16"). the service limit is 4.5mm. the 82 is 5.5mm. the 750 is possibly thicker than the 650. the 1000 has a dual disk Fr brake. could be a smaller diameter. don't know. the 650/1000 csr disks have 8 rivets. some earlier disks are 9 rivet.

thanks for the response. I may have made a dumb decision and bought a 1999-2005 Kawasaki Vulcan 1500 Nomad front rotor. Inside Diameter is 130 Outside Diameter is 280 with a 7 bolt pattern 7mm thick. Sounds like it could work (possibly). its going to take a month to come in so I can come back and confirm if it works or not. Wish me luck.

is your current disk 4-bolt.  with a mounting hub riveted onto it? 

You also need to be aware of the offset between the mounting surface and the disc. The wrong offset will prevent the disc and the caliper from lining up.

It’s a 7 bolt disk. Hopefully this photo helps.

this rotors OD is 280mm but is sadly cracked. Still trying to see if I can find any replacement.

Zpower UK. Will ship world wide or Google EBC MD4038 for supplier near you. 
(EBC MD4038) 
FRONT FITMENT =  Z1000J3, Z1000R2, GPZ1100B2.
These are EBC discs, OD 280MM ID 130MM 7 HOLE MOUNTING.
www.z-power.co.uk/brake-disc-ebc-md4038
 

jackson_mitchell@outlook.com wrote:

It’s a 7 bolt disk. Hopefully this photo helps.

this rotors OD is 280mm but is sadly cracked. Still trying to see if I can find any replacement.

that's not a 750m-csr front wheel or disk. check the wheel size. should be cast into it. single disk, could be from 750k twin. or 440 or 550, or 650 from the 80s. the 550c-ltd Fr wheel is 19 x 1.85.