Honda-SOHC

Hi guys,
I've been chasing gremlins (and possibly ghosts) on my 1977 CB550K3 ever since I got it 20 months ago. Done very little riding (almost none), lots of tinkering, got burnt by a mechanic that did some things right and some other he messed up completely, I cleaned the carbs several times, changed spark plugs and caps, air filter, manifold o-rings, new condensers.....basically everything I could think of that could cause my problems.

Aaaanyway, with 30 years of Vespa riding, I am a novice when it comes to Hondas. I have a great passion for mechanics and I believe I have done all I should have done so far (mostly a 3k tune-up) to a decent level, BUT, I have nobody to be able to check that for me, so I may be chasing my tail forever.
The bike starts fine, just a little choke, and idles ok, but as soon as it warms up (2 mins or less) the idle fluctuates, with no input from me, between 1000 and up to 3000 rpms. This is a great improvement to what it was as it used to shoot up to 5k and would hang in between gear shifts, which made it unridable.

The battery is fully charged....but then again, I am not riding this often at all and have recharged several times, so it may well be the battery itself giving me problems, but I need to eliminate other things before I think about replacing that.

The last 2 things I "believe" I need at this point are
-Timing set with strobe light (I have done the static, but assuming the advance mech. springs may be a bit weak only the strobe lamp will shed true light on this (sorry, this is a terrible "dad" joke....my kids would be ashamed)
- Carb sync: I have the necessary gauge tool and I have watched several videos on how to, however I have never done before and I don't have a proper space to do it (without annoying a few neighbours...)

My question to the audience:
Anyone in North London area (I am in N5) who could help me with these last 2 tasks? I have an old strobe light and the gauges set for the sync, but never really used them before and I would appreciate an expert and watchful eye from a more experienced member.
I tend not to trust my bike too much (it's probably all in my mind) and I am weary of getting stuck on the side of the road, but there are worst things in life and I will of course travel 10-20 miles to reach you.
I will also wear a facemask and keep social distancing, needless to say.

Anyone available around here?
Alternatively, anyone knows a good mechanic around here who would do it (and knows how to) without skinning me alive?

Cheers
Michele

[Edit]
Went for a short ride today (4 miles, city roads) and I have a feeling the bike is not as sharp as it should be, it feels it can't get all the power out (and I am just opening the throttle in 1st, 2nd or 3rd) a bit like when you have something stuck in your throat and your voice's not clear.
So, re-checking points gaps and timing (will try using my strobe light) will be my priority this week.
Any other suggestions are welcome, as I said, I have no real term of reference in my experience....

Hi all,
I have been chasing gremlins on my 1977 CB550K3 and now, after a deep carb clean where I unplugged a couple of bowl breather holes and an overflow tube, the bike starts well (always has) but within 30 seconds from stone cold idles between 4.5 and 5k. When warm, just shoots up there straight away. No binding cables, the idle screw is fully off and the shaft rotates all the way to the "fast idle" screw (which I have not touched). Slides are not getting stuck anywhere.
3K miles tune up done and all the rest as suggested by this and other forums (or is it fora?), so I know it could be a series or a combination of factors that I have on a big list and will get to (it is mostly stock, but has paper air filter and 4 into 1 Delkevic exhaust, so some fine tuning will be needed), however, proceeding by elimination I wanted to check with the experts here that my slides are actually in the right position for idling. To be honest I thought they would much closer than this, but before I take the carbs off again I wanted to ask a wider audience.
The carbs have only been bench synced for now as I don't want to perform a proper vacuum sync at 4k RPM...

Are this simply too wide open for idling, meaning I must have messed up something when reassembling the throttle shaft? I have not taken the slides off their linking arms, so there is no chance that I put those back incorrectly (back to front, that is)

Apologies for the mini images...my usb camera is not the best, but it should give you an idea anyway. This is carb #2 viewed from the air box.
Many thanks for checking this out!!
Michele