With a motor, the inrush current is also called starting current. It is the current that exists when the device is new, and it gets higher when the device gets older. When the bearings are in need of grease, this can also create a higher current.
You have to be able to measure the inrush current surges so that you know the generator that is needed. To measure it, put the meter on the amps setting on a clamp meter that is able to measure the inrush current.
Push the inrush button. By running your motor, you can then see the inrush current on the meter. The inrush current is much higher than the standing current. While many people believe the inrush current is double the running current, it can be as much as four to 10 times higher. Read at least the first five cycles or so rather than stopping at just one cycle. You can then see how long it takes for the inrush current to settle into the standing current. An older motor or one that is in poor condition will take significantly longer to settle into a steady current. New devices should settle much more quickly.