The Wixom and the Bates handlebar fairings came and went pretty quickly in the mid-to-late 1970s. The 750 suffered a lot of wind effects against the handlebars from them. Many of the Bates versions ripped off their mounts in places like Colorado, Kansas, or Arizona in the fierce crosswinds that can be found in Interstate riding, and this news spread like wildfire back then. The frame-mounted fairings like Vetter and its knockoffs overtook the handlebar fairing market by about 1975, for the most part. I actually removed more of those in favor of a new Vetter than I did install Vetters on new bikes.
Today, if you go into one for the fun of it, a few things you may wish to do:
1. Install tapered steering head bearings and run them a little tighter than normal, for some damping assistance.
2. Install a steering damper, if you can.
3. Install HARD swingarm bushings, like bronze.
4. Make sure the wheel bearings are in top shape.
5. Make sure the chain and sprockets are smooth, no snatching. Tires must not have a flat spot on them, either.
While seemingly obscure, the little handling deficiencies caused by items 3, 4, and 5 above were the most common cause of speed wobbles with the handlebar fairings. Anything that tended to make the head "shake" was then amplifier by the not-steady mass of the fairing on the handlebars (they don't sit real still up there, but wobble around in the wind quite a bit).
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