Be gentle - I'm a complete newbie to the Honda CB world.
Just acquired a custom trike that has a CB750 K2 engine in it (based on the engine serial number).
So I've been going through the basic checks. Tonight I dropped the oil pan and oil filter cover in order to inspect, clean, and to put a new filter in.
Imagine my surprise as I take off the oil filter cover, and an additional hunk of aluminum comes off the front of the engine with it. Wasn't expecting it... nothing like that in any of the CB750K parts diagrams. It took me a bit of research to figure out what this is... it appears the PO put on the F2/F3 oil filter assembly, including the additional "oil cooler", which I describe as a finned spacer that is between the cases and the "outer" oil filter cover. It has the longer bolt to account for this "spacer".
As I went through parts diagrams to figure this out, I've determined I appear to be missing two parts. First is the skinny washer that goes between the spring and the filter. I actually found a washer in my random bin of washers that fits, so I think I'm OK for that... can't imagine that part is particularly sensitive to very exact specs - this one fits, and does what it would seem to need to do, which is give a nice flat surface to mate to the rubber on the filter, rather than the relatively skinny spring digging into it. I've also read that a lot of bikes are missing this anyway, since it tends to get thrown out as it's often stuck to the filter.
But the other part I'm missing is described as COLLAR, OIL FILTER BOLT. Part # 423-333-000.
Best I can figure, this item is present mainly to center the bolt in the oil cooler spacer. The hole in the center of the cooler/spacer is much bigger than the bolt. Without this "collar" it would be pretty hard to ensure the oil cooler is centered and gets a good seal on the engine case. I suppose it might also hold the filter tight against the spring. Photos I've seen of this collar show it fits right into that opening. Here's a good example - the oil cooler and the collar together:
https://www.ebay.com/itm/HONDA-CB-750-K-FOUR-1969-76-OIL-COOLER-HEAT-SINK-PLATE-SPACER-DRAG-CHOPPER-RACE/402136700432?hash=item5da1371610:g:1LcAAOSwwaVeXtBPHere's the odd part - On the engine case itself there seems to be a "boss" that protrudes, on which the oil cooler ring centers perfectly. It seems THAT would be the collar... but unless it's just REALLY stuck on, it seems to be part of the engine case.
So what I need to know - someone with an F2 or F3... can you tell me if your case has that protruding boss? If so, do you have that AND this collar? Can you give me the measurements (length, I.D. and O.D.)? It would seem I need to find or make one of these. That said, I don't actually know how this would work... It seems that combining that collar with the boss would press to filter WAY too far into the filter cover, completely compressing the spring, and thus covering the "bypass" holes at the top of the bolt.
FWIW, The only place I've found to buy this collar is a repro from Germany.
Oh... this same collar appears to be a part on the CB350, as well, although the CB350 doesn't have the additional finned oil coller ring.
