Having owned my 1985 K100RT for 35 years, I am no stranger to the vibrations of the exhaust guard. As my bike has aged, the flimsy captured nut retainers have broken bit by bit, and sounds loud enough to wake the dead have been experienced throughout the decades. I would adopt some "fix" and it might last a season, only to have to try again some months later. Short of getting the OEM repair kit introduced some years later by drilling and inserting threaded pop rivets where the captured nut retainers are- a kit that took me fifteen years to find, I finally was given what I thought was a skeptical solution by my older brother.
At seemingly any hardware store, GE Clear Silicone can be found in tube form for under $10. With the guard removed, and no matter how little of the captured nut retainers are left on the exhaust, flood the area liberally with the silicone- including the nuts. Likewise, on the underside of the guard, run a bead where the guard sits atop the captured nut retainers. Do this for every attachment point. Allow the silicone to "skin" up for no more than ten minutes, then mount the guard and secure. Allow to cure for at least 24 hours without running the bike.
What happens is not only is there a bit of extra adhesion of the guard to the exhaust given by the silicone, but it also must fill any void that will cause vibration! What I was skeptical about actually works! The silicone can take the heat- there is no smoking or odor, and the bike is quieter than it has been in years! I don't know what it will look like when it comes time to ever remove the guard, but the vibrations are fixed!
