I used to have the exact same problem you are having except I had an OS 40 FP and from what I can see from the LA engines there isn't too much difference except the color and the shape. I would fiddle with this stupid engine all day I would get it right on the idle but then it wouldn't stay there during the flight it would either idle too fast or die completely. I got so sick if this engine I took it off and deposited it in the dumpster and bought a OS 46 SF and a Super Tigre GS 40 best investment ever. I only have to set the high speed needles for the first flight of the day and never had to mess with the idle it used to suck having to fiddle with a sorry engine while your friends are flying around my advise look into another engine and save yourself some grief I ahve always had good luck with the OS SF's and Supertigres as far as 2 strokes go and I use Saitos for my 4 strokes, get engines with Ball Bearings those brass bushing are cheap and for a few dollars more you get more power. Another option fi you really don't want to get another engine that I have heard works is replace the stock carb with a Perry carb.