yep, offset of the shaft is critical. regretfully, the 500 manual only list clearance between rotor and housing, not diameter, so no answer, but i would tend to believe that honda used a single rotor dia/shaft offset for all models around that time, chnaging only width. Kaz Yoshima used GL1000 rotors modified for his 400 for exmaple, but i dont have solid numbers, my oil pump is already mounted..