lol I know how it is having problems with a bonne
Make sure your coupler is the culprit though. Check your pulley for play by putting a wrench/ratchet to the tensioner to loosen the belt.
Since you asked, I will take pictures the best I can and document the process free of charge. I'm not going to charge you any money simply because I would appreciate someone doing the same for me. All I ask is that you do the same for someone else somewhere down the line. I only consider this job rather easy because I had the SC apart before to rebuild the nose drive, and was holding the bad coupler in my hand at the time. I didn't know it was bad though
First picture is the coupler. It has 6 holes. 3 metal rods from the nose drive go into one side, and 3 rods from the "propellers" from the inside go into the other 3. Over time the holes wear and become an "oval" shape thus giving you play. I have read that even the slightest bit of play can cause noise. My noise is a loud rattling sound coming from the middle, bit closer to the pulley of the SC. Lower the RPM the louder it seems to be.