There are two windings in the cutout, a series winding and a shunt winding. The magnetic field from the shunt winding causes the cutout to "pull in" when the output of the generator reaches a certain voltage. Current through the series winding helps to hold the cutout "in", once it's pulled in. When the engine is shut down, and the generator stops charging, the voltage holding the cutout "in" drops, and the spring is trying to pull the points open. Also, the current through the cutout's series winding reverses 'cause the current is no longer flowing from the generator to the battery, but is now flowing back into the generator, causing the magnetic field it produces to reverse, cancelling out the magnetic field produced by the shunt winding. This gives the cutout a split second to "drop out". So, the action of a cutout to "pull in" or "drop out" is a balancing act of the spring tension, the "air gap" between the points lever and the core, etc. The original cutout would have had an adjustable air gap, and adjustable spring tension, and the shop manual would give the "specs" for these, and give a "spec" for the "cut in" and "drop out" voltages. With today's imported cheapy units, and the lack of a local "mom and pop" electrical shop to set them up, about the only thing to do is hope you get a GOOD new unit!
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