When you remove the starter, the part that goes inside the bell housing holds the end of the shaft. The gear assembly that you can see on that shaft is the bendix. If you turn the gear one way it will push out (away from the starter motor) on the shaft. It should travel smoothly (it is spring loaded) and go almost to the end of the shaft, if you try and turn it the other way it will not move. Look for burrs or rough spots on the shaft, if you find any use (fine 300 grit or up) sand paper to smooth out and then light oil.