Two Strokes do tend to Load up at Lower Speeds, Nature of the Beast, but an Overly Rich Mixture will certainly speed that up.
Factory Spec? There is an Initial Setting, that will allow the Engine to run, a bit on the Rich Side.
The final Setting must be done with the Engine Warm and under Load. There are a variety of ways that are used, and everyone will swear theirs' is the Only Way.
My way was to have the boat in the Water, in gear, either puttering around, or have the Stern tied to a very Heavy Anchor, or a solid Dock. I would start with the Initial Settings, and Lean each Carb, individually, Rpms will go up. When the Rpms start to drop, I would make a Note as to who far in I turned it, return it to the Initial Setting, and move on to the next Carb. After I had done that to all, I would then compare the Responses which I had noted. I would then turn each respectively 3/4 way between the Initial Setting and the Lean Stumble. Then I would run the motor at the speced Idle and repeat the Process, but this Time, adjust for the highest rpm, and then returning to the Speced Rpm, Repeat for the other Carbs, then go thru it a couple more times. After, check Acceleration, if it Bogs, open all Mix screws up an 1/16 turn
