Well, also, bikes with big windshields and panniers aren't really made to go fast, even if they sometimes can. That's what fully faired sports bikes are for. You frequently see aftermarket panniers rated for 120km/h, which is 75 mph.
So if you have a swaying at 120 mph, your actual problem is that you're going at twice the maximum legal speed.
I have had my Triumph fork mounted shield to at least 140m/h without issue.
It is even raised 1 inch higher than max allowed.
I'd check: Gooseneck bearing adjustment - loosen and realign triple clamp bolts - tire brand, pressure and cupping - remove all weight attached over rear fender . . .
EDIT -
I be a dum*** as this is R3T related, not R3R!!!
Please disregard my first sentence.
Yeah, I'm not a fairing fan in general, but the Corbin one is almost nice. Corbin claims the design actually stabilizes the front further compared to no fairing, and I can see how, ie acting as a rudder.
As @1olbull said...check the bearings in the neck and if it is still running a Metzler front tire get rid of it and get something that stays round. Every metz I've had cups fairly quickly and isn't readily apparent until inspected very closely. @Steel had a high speed wobble that turned out to be the bearings in the neck. That would be my first look
I have a shop manual. I'll review the procedure and check the bearings. Seems that's a common issue. I just didn't expect it to be a problem with only 1400 miles on the bike.
As @1olbull said...check the bearings in the neck and if it is still running a Metzler front tire get rid of it and get something that stays round. Every metz I've had cups fairly quickly and isn't readily apparent until inspected very closely. @Steel had a high speed wobble that turned out to be the bearings in the neck. That would be my first look
I have a shop manual. I'll review the procedure and check the bearings. Seems that's a common issue. I just didn't expect it to be a problem with only 1400 miles on the bike.