Locate the cable adjuster at the bottom of the throttle handle. The throttle handle usually has a lever that allows you to control the speed of the mower's engine. The cable runs from the bottom of the throttle handle.
Turn the throttle adjuster counterclockwise one turn to tighten the cable. Use pliers if you can't get a good grip.
Turn on the unit and test the throttle cable. If the engine is "slipping," or not responding to the cable adjustment, turn off the engine.
Turn the cable adjuster another turn counterclockwise to tighten the cable. Continue adjusting until the engine responds accordingly.