Have you checked the "duty cycle"?

If not, go to:

www.landiss.com/mixture.htm

and print out the instructions. The duty cycle is only applicable to closed loop operation, but the basic setting is the basis for the open loop mixture when the engine is cold.

A lower duty cycle at idle means a slighty rich basic setting, and I have found that about 45 percent at idle gives good cold starts and warm up characteristics.

Duke