This occurs with one carb.while the other carb is rock solid stable.

Normal setting for my car is 1 1/4 turns. Most recently, after 700 miles, the problem carb was down to 1/2 turn.

I tried reversing the spring but it has not helped. I suspect the spring ends have been acting like a lock washer urging the screw in.

I have been thinking about adding some thin brass washers to decouple the spring and screw.

Any suggestions?

Yes, add the washers. Most carbs I have worked on have a washer at the carb end of the spring.

Hi Pete,

 

Added a washer yesterday. Couldn't add two because the spring went solid before the screw bottomed out.

 

BTW I examined the spring ends and found that the were supposed to be ground flat. However one end had a very spotty grind and could very easily dug the end of the spring into the screw to act like a lock washer. A few strokes against a honing stone cleaned it up nicely.

 

Hopefully the renewed flat and the washer will do the job.