Few problems after reassembling...

[O.R.]

..maybe the oring in the slider guide? Ultrasonic cleaning might have moved it or damaged it...?

I hope you dropped the carbs in the ultrasonic cleaner disassembled

Ultranic cleaning leads to a lot of fine rubbish. When carbs are "cleaned" without disassembly, a lot of dirt will be "trapped" behind the fuel/air jets.
In that case, your air jets could be clogged.

I am now thinking of the main needle, might be worn!

A worn (jet) needle can be identified by just looking at it.

[Yuza]

He did it, same mechanic whom I brought the bike to...
The needle didn’t look worn when he dismantled the carbs before cleaning, otherwise I would have replaced it.
I would bet my money (which I will need to spend soon to pay for the job so no bets...) on the slider guide o-ring.
At least it would be cheap....well, finger crossed

[Yuza]

It works!!!
Many hours (and many euros...) of trials and the reason of overflowing was so stupid.....

One of the previous owners replaced the washers below and above the seeger which sets the height of the jet needle with others with wrong internal diameter.
This resulted in the needle seeger passing over the upper washer from time to time and remaining blocked in a much higher position, normally just after opening a bit the throttle.

The mechanic replaced the washers with proper ones and now it runs fine

[Yuza]

Here it is, almost finished

[H_Lime]

Looking sweet Yuza, bet you cant wait to s2ing a leg over her!

[Yuza]

I do indeed, but I have to wait because it is snowing here...

[Monodoggie]

Glad you got it running, bike looks really nice

[nug]

Nice

[Deano]

Looking good and great to see another lovingly returned to the road

[Yuza]

Hi all again, I did not have the chance to ride it properly yet (snow and rain every f***ing weeken since I completed the rebuild!)
But one thing I noticed is a little surging at low/mid revs
I have a new header from ebay (unknown brand) and a Marving exhaust, stock jetting and airbox/filter
Do you suggest any different jetting?