There were 7 plates in pack on bike, vendor provided 7 thinner plates and an additional plate of equal thickness, but with wider “tabs” which in no way would fit into slots in basket.
Sadly, this is commonly confused at the vendors: I get to 'talk' with a number of them from time to time when their inventories get skewed up. They are usually good about straightening them back out, but then they probably forget, or get "that new guy" who doesn't know, and they get mixed up again. I've had best results with the guys at PartsNmore.com as far as getting them "straightened out" again, but since about 2005 when I first met them, it has gotten mixed up at least 4 times again. The 750 suffers this a little bit, too, but it only uses 3 different plates, all the same thickness, so it's simpler there.
In the "slipper plate" clutches, there are just 6 of the narrow-fingered ones and 1 of the wider-fingered ones (on the top of that hub's stack). The wide ones are usually the "slipper plate" type in so-called "corrected" clutches, but many of the 500K1 and 550K1 and late 550F2-3 bikes started getting the slant-cut ones, though not regularly in my observations. They always slip more on startup: that's their purpose.
But, what sometimes happens is: the installer may not realize that the clutch spins backward from the crankshaft, and then they get installed backward: this constantly traps oil between the plates aggressively, making them slip almost all the time. So, make sure the "pinwheel" tip is pointing opposite the crankshaft revolution (outer edge of gap to your right as you install them) before chasing new plates: the slant-cut ones will work if you have good oils and the rusty stuff wipes itself clean (after a while of riding). I don't always rush out to change the plates if I can ride the bike at least 50 miles and see if it gets better: often the rust will flush away, especially in the slant-cut plates. If they are real rusty they might not slip very well at first, and that crusty stuff WILL go thru the oil pump before the filter, so removing most of it should be important.
I will name the vendor here how keeps selling the wrong plates, and on purpose: it is Vesrah. They are advertising a 1-size-fits-all 550 clutch which will not, and cannot, work in all the 550 engines. Reason: their supplied springs are extra-strong in case you started with the thicker-plate clutch and now install their thinner ones: this causes almost 20% less spring pressure with standard clutch springs. That makes the clutch slip. BUT -installing the stronger springs from their "kit" overpowers the fragile lifter of the CB550 case, causing it to either insufficiently lift the pack free, or causes the owner to try to adjust the lifter tighter, at which point it goes 'over center' with a loud "snap" sound, leaving the clutch fully engaged with no disengagement possible until the cover is again removed and the lifter reset. This is epidemic in the CB550F (Euro CB500F) engines, and I hear about it A LOT. Because of that fact, I spent several pages, in more than one place, explaining it in this new book.
I've asked Vesrah management twice (once by email, once by snail mail) to correct this, but it is falling on deaf ears, from my seat.
You can get correct thickness plates from PartsNmore. Honda's shops will not always send you the right ones, either, because the parts personnel are younger than your bike, and they haven't been trained on the details of the 4 different clutches in the CB500/550 series bikes.
Back when I first published My CB750 Book the response was huge, and fast. I 'used' that, by 2008, to establish a dialog with Honda, PartsNmore.com and CB750Supply.com to help them get us some corrected parts for the 750 back then, and label them correctly on their websites. I'm kinda hoping this will happen again with My CB500/CB550 Book, at which time I'll try to re-approach Vesrah (in particular) to educate them so they will stop ripping off these bike owners: the clutches are not returnable once installed. I, too, am an engineer, and likely for quite a bit longer than the ones who are telling these vendors that "this is OK" when it is not: some new engineers simply lack the needed experience. At one point I had a 2'x2'x2' box of slightly-used thin Vesrah 550 clutch plate packs (about 49 plates) that others who asked me "why does my new clutch slip?" finally got the RIGHT plates, and then sent me their WRONG plates in case I could use them. I don't work on that many 1976-77 550F engines that use those thin plates (just their top ends show up here), so I finally gave them away for more space. It turned out that some 1990s superbikes also use those plates (in different numbers of plates/clutch), so they are everywhere.
