Dear Redfox,

Thanks for the reply. My WM P51 Model A155 weigh 4 kgs without fuel.  A local friend of mine advise me not to play or close the needle valve
to much to lean the 4-stroke.  He said, it is not really good to lean out or close the needle valve just to get the right RPM of the engine or propeller I am testing.

At the moment, my needle valve seeting if just at 2 turns (from fully close).  I believed my OS fs110-a started from 3 to 4 opening of needle valve from fully close.

Will it damage the engine if I set the needle valve to 1.5 from fully close?

Also, another question, I also have WM P51 size 46 engine is OS 55AX and I installed a 3-blade propeller 11x8 with tru-turn spinner.
Can I get your feedback about this combination?  I flew it twice......so fast with Apc 13X6 propeller.  Now, I tried to enabled flaperon and hoping it will slow it down plus the help coming from 3-blade.  WM P51 size 46 doesn't have FLAPS.  I hope have seen this model.

Thanks again for your support and constructive comment and feedback.