The governor is a speed control device and does not "kick in" - it functions constantly.
The throttle cable (indirectly) pulls on the governor spring that's attached to the lower part of the governor lever. Pulling the lower part of the lever causes the top to move away from the carburetor, which opens the throttle plate via a link between the arm and the throttle shaft.
The centrifugal weights and thimble on the governor gear respond directly to engine rpm. As the engine speed increases, the weights cause the thimble to move outward against the tab on the governor cross shaft, moving the top of the governor arm towards the carburetor - closing the throttle plate.
When the spring tension and the centrifugal weight force equalize, the engine speed remains relatively constant.
If a load is applied to the engine and the rpm drops, the weights and thimble retract (against spring tension), allowing the throttle plate to open.
This "cycle" repeats indefinitely as long as the engine is running.
Providing all related parts are correct, present, and in good condition, it may only be an adjustment issue. If you synchronized the governor lever / cross shaft per the manual, it's possibly a throttle stop or cable adjustment issue.