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Hi Paul,

The OUTER rings on the plugs are rich, but as you know that can only really be adjusted via the man jets / air filters.

The Electrode and Strap look rich on most of the plugs, so probably Primary / Enricher Circuit issues such as channel blockages.
You can still get a decent reading on a Colortune Plug with Primary issues and blockages but it will constantly change as a result until they are 100% clear.

If you have had your carb bodies ultra sonic cleaned, dont believe that will necessarily unblock all the Primary Channels inside the bodies.
The only ay to be sure is to leave the bodies in a bath of cellulose thinners for a day or 2, so it 100% disolves any blockages..............you will be amazed the difference it makes even after sonic cleaning...........still full of crab it hasnt removed.

Pete F
UK

Oh the Yin Yang of engine dynamics and how to properly tune.
What I see- All the plugs except 5 show signs of oil ingress and not being completely burned off leaving a wet shiny black appearance around the center electrode insulator. Could be the rings are not seated yet or valve stem seals on the intakes are allowing oil past the valve stem/valve guides. But if I remember right, you had the head rebuilt.
#5 is not burning oil AND it's running on the hot side of what I like to see in a carbureted engine. If it was a fuel injected engine with O² I'd say it's perfect but in a carbureted engine it's running on the hot side and no room for mixture error based on ambient temperature, barometric pressure and engine temperature. Carbureted engines should have brownish colored electrode insulators which indicates good engine temperature, little to no oil burning, good burning of the fuel and proper heat range of the sparkplugs. If I was doing a tune up on a carbureted car and I knew the owner was a "Little old Lady from Pasadena" and only drove to the grocery store once every 2 weeks, I'd put in a set of hotter sparkplugs to help burn off the wet oil residue, but I would not do this in a motorbike because motorbikes have smaller engines which tend to run more in the midrange/power on mode than a car used for grocery shopping in town. Even a well tuned 2 stroke will have brownish center electrodes but the oil used in 2 strokes is reduced ash oil. Black and wet center electrodes- running rich on fuel and oil ingress and just not burning it all off. Yin Yang.
That's my 2 cents

Thanks both.

I did have both the head and the carbs rebuilt by Oz and the valve stem seals are brand new, so I would expect the carbs to be as clean as they can get, and the head as good as it gets.

However, I am still running this engine in (only 250 miles to date) so it may need more time to 'settle in'. Also, because it has not yet been run it properly, I have not been caning it and most of the time running at below 2500 rpm, so that may be another cause of slightly dark plugs. I have had to put another 1/2 litre of oil in, so it has been burning some..

AND I am not running the standard air filer, but four K&N pods, so maybe it needs different-from-standard jets...

I will adjust the mixture on number 5 to run a little richer to bring the temp down and leave the rest. Then check again with a few more miles on the bike (summer next year judging by the weather and Covid etc)

Cheers
Paul

Just went to adjust mixture screw on cylinder 5 and found it had worked itself loose completely, only gravity kept it in there!

Now re-adjusted to 2.5 full turns from closed, with a little Locktite applied!

Pfew!

If it's not too late why not try putting some silicone over the screw that way if you have to make an adjustment later it won't be a pain due to the loctite
Just my thoughts ( 2 cents worth lol)

Thanks, the stuff I use stays tacky, and hopefully no more adjustments needed after this..