Typical motor problem, The data is from the NEMA standards

If the motor is a the usual split-phase type, the 4 wires should be the connections to the run and start windings (2 wires each). I think the yellow/black wires go to the start winding, but it is better to verify this as follows. First, you need to find the centrifugal switch which turns the start winding on/off. This switch is in the "ON" position when the motor is NOT running, when the motor gets nearly up to speed, this switch automatically dissconnects the start winding. Usually, the switch is operated by a spring-loaded plastic collar on the motor shaft (on the end where the wires enter the motor). Look into the end of the motor and find it using a flashlight, you should be able to push down on this collar with a screwdriver and activate the switch. Pushing in the collar turns off the switch. Check the resistance to see which winding gets turned OFF when the plastic collar is pushed IN; that is the start winding. The winding which this switch does NOT affect is the RUN winding. Note: you will need to disconnect the two pairs of wires from each other to make this test, as the two windings are wired in paralell with each other. When you are done, one wire of the start winding will be connected to each of the run winding wires. For example, if the two red wires are found to be the run winding and the yellow/black are the start winding, it would be: one line wire+red+black hooked together and the other line wire+red +yellow hooked together. If you need to change the direction of rotation of your motor, just interchange the two start winding wires. Note: the normal resistance of these windings is only a few ohms.