I need rotors for the 1999 GS500 I picked up. My 1989 Katana 750 look very similar. Any idea if they fit.

A quick check with the tape measure says no.  I also have an 89 Kat 750 and a 2000 GS500.  (weird)  The Kat disks are almost an inch smaller in diameter.  

Does your Kat run?  Were you thinking of canabalizing for parts?  Mines in pieces right now but I am planning to put it back together.  Right now I am fixing the plastic and waiting for powder coating.  

Rob

I just bought both bikes from different people. The Kat needed a left rotor so I bought both. The right is still useable.

My kat needs front tire, rotors, signals and a battery.

The GS is nasty. http://home.cogeco.ca/~gvanhumbeck/1999gs500.htm