Just for argument's sake even though the charts say Wisconsin does require, if you read the statute it does NOT require signals on motorcycles. I found some reference to "on or before jan 1 1973" And I think that goes with what I have seen on 70-72 XS650s including brochures, that the signals were "installed on request"...
Seldom does law or insurance require you to retrofit equipment not required when the vehicle was new. I see old pick ups with one brake/tail light operated here.
WI stat. 347.15 Direction signal lamps or devices.
(1) No person may sell any new motor vehicle, other than a moped or Type 1 motorcycle, unless such motor vehicle is equipped with direction signal lamps meeting the requirements of this section. No person may operate on a highway any motor vehicle sold new after January 1, 1955, or any mobile home, or trailer or semitrailer sold new after January 1, 1968, other than a vehicle which is operated pursuant to s. 341.47 (1) (b) or a moped or Type 1 motorcycle, unless such vehicle is equipped with direction signal lamps meeting the requirements of this section.
Changes and improvements from the XS1 were among others :
Some small changes on frame, new front forks ass'y without the rubberboots,
new tail lamp unit, rear fender stay, flasher lamps as standard equipment (only alternate parts on the XS1)
The Yamaha parts fiche confirms this.