Honda-SOHC

I do find it confusing that the 500 & 550 are grouped together here.
My 500 needle was in the middle when dismantled so that's how it went back.

It shouldn't make a big and fundamental difference Ted, it's really fine tuning in those steps to set the needle and won't as such give the fault experienced here.

All it does is move the mid range throttle fuelling up or down a little to tweak response or cope with plugs just a little too dark etc.

Clear fundamental issues in mixture will come from wrong spec or worn components to give the bigger steps of error seen so far.

Go for it, great bikes.
First the bad points:
1. They are heavy, something like 210Kg fueled up. This makes them a bit of a lump to move around in the garage. The weight disappears when on the move.
2. They run bloody hot. This is because RE had to run them lean at the rev band where the emissions tests are taken.
3. The OE seat is worse than a 400/4 plank.
4. They are built to a price and some parts of the bike show it BUT not in finish, only in choice of materials used.
5. The suspension front and back is basic but if you are used to a 70’s Honda you won't notice. Everything is available (for a price) to have better suspension.

The fixes needed to make a great bike even better:
1. Ditch the entire exhaust system, not just the silencers that weigh 7kg each and both contain cats but also the very restrictive header pipes. Replace with S/S TEC 42mm big bore headers and a pair of S/S Cannon silencers. The result will be instant, a lovely sound and better breathing.
2. Throw the OE seat in the bin and replace with the RE touring seat, your piles will thank you for it.
3. Remove the air box snorkel and the paper filter and replace with a free breathing K&N, don't replace the snorkel.
4. Fit a Fuel-X unit but not the all singing and dancing programmable unit which is IMHO a waste of money. The standard Fuel-X is plug and play. It looks the Fi system into thinking it is running lean at low revs (where the emissions tests are taken) to make it pump more fuel in. This results in a cooler running engine, better pickup and free breathing.
5. The OE footrests, gear levers and brake levers are cheap and nasty painted steel. Fit TEC alloy units that are adjustable, look so much better and don't catch your trouser bottoms!
6. The above also applies to the brake and clutch levers, fit a pair of TEC adjustable units to give you hands a decent span.
7. OE mirrors are pig ugly and don't do a very good job either. A pair of stainless bar end mirrors from Stadium are great and are available from Hitchcocks who also sell the special bar ends you need to fit the stadium mirrors. Very, Very cool😎.
8. Fit a fly screen, the RE is the best as it fits without modification to the headlight brackets. They do work and protect the clocks from bugs but it does a good job of deflecting the wind off the rider.
9. The grill over the oil cooler is laughable, replace with a TEC unit.
The journalists at the time slagged off the OE tires, they are 100% fine, it's a touring bike not a GP replica!
10. Change the oil at the recommended service intervals DONT miss them. Use an ester based oil and change the filter every time. The oil (I use Silkolene) is something like £55 for 4 litres on-line, not cheap but worth it as I've heard of cheaper oils not giving very good fuel economy (?) and needing topping up.

They are easy to customise to your personal taste.

They really are great bikes, cheap, well made and a lot of bang for your buck👍

If you've got the carb bench sync routine completed to good level, as Bryan's posted routine, then there's no need to change that in "tuning" operation subsequently.

Its easily good enough, when done competently, to give perfect results. Changing it with the use of gauges brings the risk of leading you the wrong way IF there's other elements that affect vacuum accuracy.

Broadly speaking EVERYTHING else in setup needs to be verified and accounted for BEFORE even considering using gauges on it.

It helps with all the other settings to know that the sync is competent in finding other faults.

Ok here's a little update. I've found a set of 069a carbs which are of another bike i own but are in a terrible state. I've stripped them down today. The needle is stamped 273004 which seems correct for an 069a carb, according to the book.this needle is faster than the 272304 needle that's in the 022a carb and will not fit into the throttle valve from the 022a.
To my OP, the new needle in the refurb kit still doesn't fit in the throttle valve of the 069a carb so i guess that's an issue I need to take up with the vendor of the kit.
Today's thought: the bare carb bodies of the 022a and 069a look identical. The only identifying marks are casting inside the float chamber that says A-2. This is present in both carbs. The 069a carbs are in a terrible condition,  with lots of corrosion inside the passageways.  The 022a carb bodies are immaculate. The choke levers in the 069a carbs are seriously rusty whereas the 022a choke levers are in really good condition.
So - can i build all the necessary 069a parts into my 022a carb bodies,  using the 022a choke levers and shafts but the 069 throttle valves  along with a decent set of new 069a jets, needles, etc.

I thought that for a UK bike, the middle position was correct, US  models were one ring position richer.