Honda-SOHC

(sigh) A CB550F3 neger existed. Show me one Honda document that mentions a CB550F3. It's US craziness from a US book. They just can't believe a model runs for more than one year. In Europe succesful models ran for many consecutive As always the answer is in the appropiate parts list. They are all at Honda4Fun.com. Page 4 of the CB550F2 parts list identifies yours: https://www.honda4fun.com/dwnload/Part-List/CB550/CB550-F2-Parts-List.pdf
So: a CB550F2-E

I bet there's a three digit number on the inner side. 341?

Some bargains at the NEC today including this beauty

https://www.iconicauctioneers.com/1971-honda-cb500-four-k0-rec16195-1-nec-1125

That is is not original paint, is it? Peculiar positioning of the brake actuator rod.

Depends. What is the prescribed position and what is yours now. I've changed the needle's position (CB500) out of curiosity and there wasn't that much effect, just like a Honda mec had said. I'd stay close to the original settings.
Leaking O-rings on the main jets have to be excluded, as well as accidently reamed slow jets.
Aftermarket air intake can make a difference, aftermarket exhaust hardly at all.
The correct fuel level in the floatbowls can easily be checked by applying this method: http://forums.sohc4.net/index.php/topic,185754.msg2151647.html#msg2151647.
Without having read all the above, make sure air intake is unobstructed, the airfilter element is good, meaning not moist or fouled by crankcase fumes.

I always use a T-handle and a 23 mm socket when cranking some millimeters a CB500 for timing. I estimate the risk of damage by removing the spark plugs far higher than cranking that WASHER, SPECIAL which, btw, is still the original... Things may be different with a CB750. I've seen more than once that problems that can occurr on CB750s, were bluntly transferred by experts to CB500550s.

Thnx!

Thanks. The reason I asked: in 46 years of ownership I remember only two times I have managed to get any grease in there. I've been lucky I guess: bushing is still fine. I should add that Honda had modified the parts involved somewhat on later models like mine, but I don't know if that has played any role.