I base my recommendations on data gleaned from the Honda Shop manuals, and observations on my collection of CBs. They are listed in my sig.
I’ve lived in California since 1969 and suffered under the new "smog control laws" as they were foisted upon the motoring public.
California led the nation in restrictive smog laws. And, didn’t turn their attention to regulating motorcycle emissions until the 80’s. Still, Honda saw the writing on the wall, and probably monitored the legislators inclinations in the halls of politics. The 77 and 78K models saw the introduction of a different carburetor, design capable of "lean burn" idle adjustments. The F model never saw these carbs in production. All my information says that ALL the F model CB550Fs had 069A carbs. All my CB550Fs have 069A carbs. And, I know one of these (my 76) was first sold in Arizona, where smog control laws lagged California by several years, and one of these (the 77) was definitely first sold in California. On the other hand all the CB550Ks were marked with 022A, referring to how the carbs were set up. As stated before, I believe these set ups were different because of the 4 into1 vs. the 4 into 4 pipes. And, I have no data to believe otherwise. Some of the after-market carb kit manufacturers also recognize these different set ups and put different parts in their kit to maintain the setup. And, while it is difficult to prove on bikes whose history is unknown. Carbs of each setup, where I was fairly confident hadn’t been compromised since new, had consistent parts installed in them corresponding to the table I posted previously.
Bryanj claims he has superior information in the form of parts books, and I have no access to those. I don’t even know the source of those books or where they come from. I’ve no reason to believe he is trying to mislead either. However, I’ve also seen no data presented from those books. Or, any way of verification and validation if it was. To be honest, I find my own data and experience so consistent and overwhelming, I just couldn’t take someone else’s offhand word it was wrong at this point. No offence, but, I need hard data. All those years as an engineer has taught me that discipline. And, simply stating the Honda Shop Manuals are wrong, isn’t enough, sorry.
I have no experience with the European models. Or, how politics and regulations somehow ended up corrupting the fairly straightforward setup number stamping vs. internal parts selection. But, I do believe that North American models were first sold with consistent internal parts no matter where in North America they were sold.
You may well be able to change a carb body and internals stamped 627B so that it operates as an 069A. But, there are unknown specifications between these two. For, example I can’t find the air jet specification for the 022A or 069A. This is drilled into the carb body, not a replaceable jet. Further, the main emulsion tube air bleed holes are unspecified for the 627B. These tubes appear to be pressed into the carb bodies, and I know of no replacement source. The parts fiche doesn’t list this as a part available separately from the carb body. And, I have specifications that show the hole sizes are different between the 022As and the 069A. Then there is the air screw whose taper is unknown for the 627B. You will have to find a corresponding setting that equals the air flow for that of the 069A carbs at factory setting. Certainly, the needles would have to be changed as well.
So, I think you need to decide on how much fiddling with the carbs you wish to perform. If you have a Dyno, and/or enjoy doing multiple plug chop tests and repeated carb removals, reinstallation, and syncing operations, then modify your existing 627B carbs. If your bike wasn’t stock in every other aspect, I’d say keep tweaking. But, neither BryanJ or I will be at your side, twisting screwdrivers and wrenches. (Well, perhaps in spirit…)
Or, you can put on a good set of 069A carbs, set them to factory specs, and go ride your bike that performs as Honda intended.
But, then, maybe BrianJ is right and all my data and research is meaningless.
You makes your choice and your takes your chances.
Good Luck!
