Do not over tighten belt, it will break the crankshaft or burn up a bearing. Tension should be about one half inch (1/2') deflection or give at a point halfway between pulleys when pressed with your thumb. 90% of the time, low RPM is caused by OLD hard belts.If there is corrosion on the points, the starter capacitor never kicks in and helps the motor to start. At this point, the other capacitor, the run capacitor continues to keep the motor running. One of the round hump capacitors helps to start the motor and when the motor reaches high enough speed the weights and springs open the points and the starter capacitor then stops sending a charge to the motor. This opens the circuit between the starter capacitor and the motor. When the motor builds up speed, the small weights on the springs swing out and separate the points. Take an emery file and file between the contact points to clean them. Sometimes corrosion will build up on them. At the end of this stick are electrical contact points. Extending from the round disc you should see a long slender piece of copper or other material, the size of a wooden coffee stirring stick. Under the cover, you will see a white plate that has the wire terminals. Use a screwdriver and small hammer to gently remove the end cover. This should be held on with 4 long bolts and nuts that run the length of the motor. Remove the end of the motor that has the wires entering it.If your motor begins to start your compressor, but slows down, stalls and then kicks the circuit breaker, you could have bad starter points.Do they look overheated? Use a capacitor tester or if not available, test continuity across the leads of the capacitor.These are the “humps” on the back of the motor. Good indication that you have a defective check valve.If motor works fine and powers compressor pump until cut-out pressure, but when the compressor cuts back on and tries to recharge the tank, it is unable to start and stalls.

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