Hi,
I had a similar problem with my CU motor.Done 108000 from new on original motor.Every year have had to "tweak" the mixture to get it through MOT emissions as it was running very rich.Carbs where replaced by past owner and have only done 5000 miles or so.Checked them and spindles are not worn and are in good order.
I bit the bullet this year and have had refurbished heads fitted and new rings as compression was down on 2 cylinders.No more advice notes on MOT regarding emissions.Hurrah!
What a transformation! Much better running,better mpg and so much nicer to drive.
Worth checking compression and maybe "decoke" of valves as running rich may not be solely the fault of the carbs.
Hope you sort it cheaply!
Would love some new dellortos but budget won`t stretch!
Good luck

Hmm How much did you say?For that you gotto be joking....
Mem No 4519
1981 2 litre a/c Holdsworth Camper