No, it should not be weak.
Do you have the schematic? Find the kicker solenoid coil near the vertically-oriented center of the diagram. Gottlieb usually called it the hole kicker coil. Follow the horizontal line to the right and locate the switches that need to close to energize the coil. There will usually be one switch plus a motor switch. Clean and adjust those switches and test again.
If that does not help, you might want to check the action of the kicker mechanicals for friction and possibly replace the coil sleeve on the solenoid.
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