Air mixture screw
You probably find on user manual position of idle mixture screw, it's under the carb, left, front. It's not very confortable to tune also, space for fingers is almost zero. Once that you found a practical system to screw it, turn clockwise writing down exactly how many turns it needed (say 2 and 3/4 for example). Now bring it back to original position and unscrew it half a turn, and test if popping\cracking problem is reduced.
Screw closed, all clockwise, lean mixture
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