'Morning!
Galfer still makes rotors for the '83. Does anyone definitively know, is there a difference between the rotors between the two braking systems? If there is a difference, what pray tell, would that be?
Thank you to those who know.
The '82 and '83 rotors have different part numbers, and the part numbers for the '83 left and right are different.
Assuming you have an '82 (I did), there are reasonable used '82 rotors on eBay:
https://www.ebay.com/itm/402308390426?hash=item5dab72de1a:g:BDMAAOxyNDxRYZCH
The single '82 rotor is a larger diameter than the '83 dual rotors. Position of the caliper mount on the fork leg differs, so rotors not interchangeable.
Dual rotors seems to look better to some folks, and they provide more stopping power but they are also heavier (unsprung weight) so choice to be made depending on whether you intend to ride sedately or aggressively. For most folks that manage to remain mostly within legal limits dual rotors would be fine, but if you intend to stress the limits of adhesion on the road I suggest a larger single disc and single caliper. The point being that a heavier wheel(tire, rim, rotor, caliper, etc.) will spend more time in the air out of contact with the road surface than a lighter wheel will. You most likely won't know the difference unless you really push the limits, especially in bumpy turns. Also it boils down to whether you prefer better road holding at speed or more braking power. Either '82 or '83 system provide adequate performance for MOST folks.
There are aftermarket rotors that are significantly lighter in weight than the original Yamaha parts.
Thank you wise ones! My gut was that the '82 being a single disc would be both a larger diameter and greater thickness, but i do not have an '83 to compare. Thank you for the sage-like wisdom.