Honda-SOHC

Thanks chaps, it's surprising how much I've still got to do though.  I think all cables will need replacing or inventive routing, new multifunction gauge- possibly a Koso, replacement side covers, brake lines and a respray.  Oh and the leather seat project that I've got my mum involved in but sadly she is undergoing constant chemo so not much into the idea anymore.

Looking good Dom. Nice to see something a bit radical 👍

Updates following Roo's request

You're making the assumption that I've said it needs more power (supplied by the Boyer ? ) which is not what I've stated.

Sorry if I did. I may have been misled by what so many believe who attribute super powers to an EI. You have shown far more knowledge. The ignition in itself is quite an ordinary process. Complicated is that we deal with 1) an idle, 2) load (acceleration) and 3) cruise. 

Question .... can you describe the failure mode within the combustion chamber which gives erratic acceleration response as you've described it ? In other words, why are you not getting a perfectly linear response with the settings you have.

I wouldn't call it erratic. Before I touched the airscrews in 1980, acceleration was just fabulous. In my memory I was constantly turning the throttle grip forward to prevent the bike from leaping like a jaguar. Later it was just good. The mec that initially has tuned my bike - either in Japan or in Holland - must have done a perfect job. Later a Honda mec - not the same - learned me that airscrew positions may need to differ further than just the +/- 1/8 of a turn Honda prescribes. BTW, in his years long experience the CB500 was the hardest to fine tune of all the CB Fours. This could relate to the special carburetor setting, models for the European continent had. I don't know. Not much later after my trip to Greece, gasoline quality changed dramatically. I remember having read an article by a widely respected professional writer for automotive and motorcycle mags - who himself owned a CB550K3 - in which article he concluded in his last line (in despair?) that "some motorcycles just don't like some gasolines". I have never asked him, but he himself may have been struggling with his CB550K3, after the arrival of the changed gasolines.

Honda never state (as far as I appreciate) that you have to use equal idle circuit settings, just a suggested start point, [...]

I didn't say Honda did, but Honda did give a range of +/- 1/8 of a turn. Some mechanics judged the difference in air screw position amongst the 4 could need to be more than that. I suppose they may have had a reason for that.

Welcome Kev, loads of very helpful folk on here mate!  Enjoy