Originally Posted by skyline

I don't think the k4 wheel as standard can match with the k7 forks. The k4 rotors are 298mm whereas the k7 front end is for 310mm rotors; the calipers won't be able to fit on.

What you may be able to do is to chuck the standard rotors for 320mm ones and then use 5mm spacers between the k7 fork legs and brake calipers to get them in the right position for the rotors.

There is a pretty good up-to-date table camparing gsxr front end specs here; http://eviltwinsbk.com/forumz/index.php?topic=91.0 just a little way down the page. Using this I'd reckon a good replacement rotor would be off a GSXR1000 K1/2.

Hope this helps...