Governors are on every single air cooled engine, from lawn mowers and edgers to generators and one man augers. They are Mechanical and Pneumatic. Pneumatic governors are powered by an external air vane, while mechanical governors are run by a gear and spool assembly inside the engine. This page will explain how to adjust the mechanical governor on Briggs and Stratton and Tecumseh Engines.
Governors should never need adjusting, unless the governor arm is removed or tampered with. But in the event that they do need adjusting, here is how you do it. A rule of thumb is the governor shaft should be turned in the same direction the governor arm turns to open the throttle wide open. For example, on Tecumseh TVS, LEV, TVM, TVXL and other similar engines, the governor arm rocks in the counter clockwise direction to close the throttle to idle. To adjust the governor, you would loosen the screw on the bottom of the governor arm and push the governor arm so the throttle is wide open. Then you would turn the bottom "clip" (which is connected to the governor shaft) counter clockwise. This will set the governor shaft on top of the governor spool. Now tighten the screw.
To adjust the governor on a 5 HP Briggs and Stratton horizontal shaft engine, you would loosen the nut on the governor arm and push the governor arm down, clockwise. Then you would turn the governor shaft clockwise also and tighten the nut.