I had trouble with mine at first too....I had to set the low end with the
engine running. The engine had been test run (supposedly) by the
previous owner....it was really out of whack. I don't know what the
actual number of turns is, but here's a tip if yours is out of whack.

Keep the glow on the plug....you can't set the engine if the fire is going
out. Set the trim for a fast idle....a couple clicks high. Set the low speed
needle until the engine is running the fastest rpm.... the real happy
idle....then close it almost a quarter of a turn. Remove the glow.

Now reset the high speed, but only use a 1-200 rpm richened drop in
speed. Check the low speed transition to throttle, and adjust only 1/8
of a turn as necessary till you get it perfect. You always want the low
end just a tad rich....like the high speed.

FBD.