so. nach ein wenig "google'n" bin ich dann doch mal fündig geworden. das hier erklärt warum und das japan modelle tatsächlich serienmässig scheibenwischer haben. hängt mit der gesetzeslage zusammen.
hier ein artikelauszug:
"After I started riding in Japan on my Gold Wing, it was apparent that you NEED a windshield wiper in Japan. You just can't ride fast enough to get rid of the rain from the windshield due to traffic, speed limits, etc. Plus, it rains a lot there, too. The factory windshield wiper equipped with the Japanese models surely looks a lot better than the aftermarket ones! Some U.S. Wingers have asked me about the possibility of installing the Honda genuine windshield wiper. Well, there is one lister on the Japanese discussion list who had added the factory windshield wiper to his older 1500, which did not come with a windshield wiper. It cost $700 just for the windshield wiper parts, plus an additional $200 if you wanted to have the windshield washer... I doubt one would be willing to pay that much. Check out this link to see how he installed the factory windshield wiper. Follow the blue URL link to go to the following pages (yes, this site is in Japanese).
http://www.goldwing.to/techlab/genuine_wiper/wiper1.html The white 1996 SE here belongs to Masa #2 in Japan. Note the windshield wiper fluid filler cap right below the license plate and a peep hole for the fluid tank on the rear fender. "