I'm so glad that there isn't a human version of that parasitic wasp...
As to the SU issue, there is useful information here:
Burlen They own the SU Brand and make all the parts, including new carbs. A number of data sheets worth reading.
If the carbs were set up "just right" before the rebore it is possible that the new engine will need re-jetting. Anything that increases gas flow may make the mixture lean.
CV carbs use the interplay between main jet and needle profile to manage the mixture. Both needles and main jets will wear and should be replaced if there is any doubt.
To be honest SU carbs, like any CV carb, once set up shouldn't need any adjustment. If they need constant adjustment something is wrong, or they may just be worn out.
