Small Engines (Lawn Mowers, etc.): Poulan SST25C Weedeater, flex shaft, clamps

Question
Fairly new machine. Used only a couple of times. The cutting head does not engage. I can start it fairly easy but bottom unit don't spin. What should I look for?

Answer
 Look where the engine clamps onto the shaft tube, it may not be all the way down and not engaging the flexshaft, if it is all the way down, then the flex shaft may be broken, which is easy to check by just pulling the engine off the tube and turning the shaft by hand and seeing if it turns the trimmer head.