In this video I demonstrate how to modify your existing Yamaha FZ-09 (2014) bar end weights to accept the 7/8 inch bar end mirrors. This produces a much better look that using the kit supplied mount rings.
Why don't you use the tail stock and a drill bit, run it up inside the part while you're parting it off, so it will catch the spacer once it separates? I'm no machinist, but it seems better than letting the lathe throw it lol
"Knock Off" is a good way to describe those. Back when I was riding in California those wouldn't have lasted two hours because I used to ride between the cars in backed up traffic. Lost a front brake handle that way once too. Jerk saw me coming in his mirror and pulled left to try and block me. My brake handle took his mirror off the door and almost dumped me when the front brake locked up for that split second. Squished my fingers pretty good too.