The start windings centrifugal switch is what I find most of the time. The points stop making contact due to burn residue building up on the points. You will have to remove the motor from the motor pan and remove the end opposite the drive end. Since there were several different motors used, let us know which motor brand and HP you have. I have found one capacitor bad and a few sets of non-contacting points when the motor would hum but not start. If the points are not clean, you could buy a points file at some auto parts stores to clean them. I have used emery cloth or fine sandpaper to polish the points when I could not find my points file.
If you have a multimeter or ohms checker, with the capacitor wires disconnected, connect the multimeter + lead to one wire and the - lead to the other capacitor wire and see if if the ohms goes from near zero to max resistance. If so, then the capacitor is good. If always max resistance, then replace the capacitor. Be sure to always touch the capacitor wires together to discharge the capacitor before touching the capacitor wires with your fingers.
nieder45 wrote:i have a problem the motor turns on but just hums, I can spin both spindles by hand but the motor will not turn either one. If motor is left on the breaker will pop. Any advice on whats wrong and how I can fix it.