I'm currently grafting 1990 ZZ-R250 forks, yokes & caliper on to my CB250RS project. I'm keeping my original wheel. The caliper and original disc align very well, however my disc is 240mm. The specs I've seen for the ZZ-R range from 276-300mm. Can someone confirm the size please. I'm thinking it should be 276mm. The forks are 37mm not the 36mm version. It appears a disc from a CB750F has the correct offset, fitting and is 276mm. Cheers.
Here's a new metal gear one. It's 260mm OD http://metalgear.com.au/mgear-brake-disc-front-right-p-5034.html
Much bigger than that......trying to post image so show you. zzr250 caliper cd250rs wheel by Groovii D, on Flickr