I wasn't paying close attention to the headset on my winter bike, it loosened up a little and then the carbon fiber steerer tube developed a groove where it was rocking back and forth into the (sealed) bearing housing. S#it. This really sucks. I can't snug it up anymore and a new fork can be many multiples of what I want to spend on this bike. Maybe JB Weld to the rescue?
Blue tape applied to help contain the mess and reduce the sanding.
After the epoxy dried, I removed the tape.
I then reapplied fresh tape to either side of the patch; I'm going to sand the tape all the way down to the c/f tube
and no further in an effort to keep the tube concentric with no flat spots.
I started with 180 grit self stick paper attached to a new paint stick.
I'm down to 400 grit here, and I'll final polish it with some 1000 grit.
This groove was only the thickness of a piece of paper or two, but it caused the fork to rock a little no matter how carefully I adjusted the bearings. No bueno for any bike, scary on a plastic bike.
I'm very pleased with the results. I can't feel any groove with my thumbnail and since most of the force on a headset is at the fork crown where the steerer meets the blades, I think this should work out OK. Time will tell, but the bike is back together and the headset is snug but the bars turn smoothly.