Have you gone thru the initial needle settings for both high and low needles?
Have you checked the reeds for proper seating if it uses them? If it has reeds, even a small air gap between the reed and reed block can cause loss of crankcase pressure and or vacuum, resulting in low volume of fuel being drawn in at low speeds, making the mixture too lean and subsequentially making the engine starving for fuel at an idle. There is a post in the forum here on a remedy and what to look for if that seems to be the problem.

John