I had not noticed the sleeve either. Wonder how I got all the units to work that I did. I spent a lot of time making sure the cone would ride up and down, and the pulley seems to have a spring-like action and obviously it was the rubber doing this. One or two may have been missing, I had a lot of trouble with one in particular but got it to work, two years ago. The cone needs to be clean and slick. If it is then everything works better, and every one I've seen was dirty and messy. I've got another one now, will take a look soon as I can get to it. I am going to try DeOxIt-with-lubricant on the pulley next time, work it repeatedly, blow it dry with a duster, then dab the belt-contact blades with pure isopropyl and allow to thoroughly dry. There is so much friction here it won't bother the belt especially if I take precautions, and the DeOxIt will definitely have a cleaning influence.