I have heard the ridiculous situation of carburettors with the non adjusting screws are set to meet optimum emissions when they leave the factory and meet the rules when they come out out the box. They don't consider that they inevitably need to be readjusted after a short time of use, so become worse over the life of the machine of they're not readjusted somehow after time in use.
We may as well be running them on brown coal granules.

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!