Some help please with setting the idle mixture. I have tried the YS Doctor's instructions but my YS does not indicate anything wrong as per the YS Doctor, and the idle is rough and unreliable.

91FZ, OS F plug, 20/20 fuel, APC 15x7, engine mounted inverted. Motor is now run in, about 20 flights, the air bleed screw and regulator are as they were when I bought the engine, I have not touched them. Regulator screw is not flush with the body, it is slightly proud of the body. Top end is around 8.9k rpm. Throttle response through the range is generally good though there is a point around 1/3 throttle which is harsh. If I close the throttle completely the engine stops immediately. So far, so good. Anyway, I can get it to idle at 2k rpm (just) but it is not smooth, it is bouncing around 1.8 - 2.2k rpm and in constant danger of stopping. If set at a fast idle say 2.5k+ rpm, then after I untie the model, stand up, put Tx strap on, the motor suddenly quits, no revving up or rich spluttering, just a sudden stop. The YS doctor says to adjust the air bleed depending upon whether the engine speeds up or slows down in the first few seconds from 2k rpm, but it is not doing either, it just idles really rough. So I am unsure what to do. I can just try altering the air bleed one way or the other and see what happens but I hope that one of you will already know the answer.

Then if opened up gently it responds but at around 1/3 power it runs rough again and slight revs drop, is that the regulator? A bit rich or lean?

To adjust the idle on a normal 4 stroke I just treat the idle needle/air bleed like the main needle and adjust until the revs peak, it works perfectly. Will that technique work on the YS since I can't discern any revs rise or fall as per the YS Doc's instructions?

Thanks for any help,

Harry