ORIGINAL: Sawtooth
I am a beginner with my first trainer. I am wonder what the trick is in setting the carb so the engine doesn't stall. I did the suggested break in (it's a OS-46) and have about five flights but not one that the engine hasn't quit. I've read about the high speed and the idle setting but not what the engine is suppose to act when the setting is correct.
Hopefully you haven't played with the idle screw, it will be a lot easier if you haven't played with it. The majority of OS engines RARELY need the idle adjusted until you have about 3/4 - 1 gallon of fuel through them.
Assuming the idle screw is untouched, adjust the high speed needle valve to peak the engine. Now back it off (richen it) about 1/8 turn. With the engine at full throttle (a helper is handy here), pick the plane up and point the nose straight up AND HOLD IT THERE FOR ABOUT 30 SECONDS. If the engine sags and/or dies it is too lean. Open the high speed needle valve another 1/8 turn and repeat. Do this until there is no difference in engine rpm when the nose of the plane is pointed straight up.
The idle and transition (going from idle to full throttle) is something else, however setting the high speed needle valve as described above USUALLY improves thr transition.