Update: I have attached a simple picture of the fix. Photo credit of rustyrescuecyclellc on eBay. The red marks show where four small orings can be installed to help shore any looseness in the basket assembly.
I recently stumbled upon an alternative fix to the CB550 clutch noise issue. On the forums, the documented fix to this problem is to shim the plates in the basket to shore up the wear that the clutch plates produce on the basket. I have a daily driver 1974 CB550 that I perform all the routine maintenance on as per the manual. Despite this it has always had a very pronounced clutch rattle at idle that took away from the bike.
Recently, I had the clutch cover off (don't ask) and decided to attempt the forum's solution. Upon inspection, my clutch plates hadn't wore much in terms of creating slop in the basket, so the proposed solution wouldn't help. What I did find once I disassembled the clutch basket was that the metal backing plate that the bolts screw into, poorly fit in the basket. It had too much room to bounce within the basket. To fix this, I put four small rubber orings 10mm*2.4mm on each of cylinders that have the bolt holes. I pushed them all the way down to the base then reassembled the basket as usual. I put the cover back on, adjusted the clutch, and was very pleased to find that the clutch noise was gone. I don't know about the longevity of this fix, but it has held up so far.
Hope this can help someone else. (Sorry, I should have taken pictures. Hopefully it is straight forward enough.)
