Hi, I have a pair of OS FX .25 I am breaking in to fly in my TwinStar. One engine is ready, but the other has developed a problem I have not come across before. While adjusting for optimum rpm, it allowed me to completely close the needle valve without stopping. The engine ran perfectly, and did not get hot. It behaved as though the engine was set for optimum running. The suggested needle setting is 1 1/2 turn out. I would appreciate any help or suggestions. I have found nothing wrong anter checking and re-checking. Many Thanks for your opinions. Rich