I recently got my first RC airplane which is a Hangar 9 Solo Sports with the OS .40 FX and a Futaba 6EX 2.4 Ghz ( Futaba 3004 servo and 1100Mha Sanyo Rx batteries. ). I have a question about the motor. The way I understand it is the side long needle valve is the adjustment for the full throttle RPM setting and the small needle valve on the opposite side is the mixture control valve. I had some difficulty but I was able to adjust the motor correctly I think. The iddle is 3900 RPM and 12800 at full throttle and no hesitation with any transition and the iddle is smooth. I may be a bit too rich but it's a new motor so I will keep it there for a couple of flights. Now, I want to know what is the purpose of the longer valve on top of the motor ? The manual say : "Throttle stop screw" but they don't explain anything about that one.

Thanks,
Séb