When your Briggs & Stratton engine seems to be using a lot of oil or you actually see an oil leak between the engine block and crankcase cover, then it is a good sign that you will need to replace the crankcase gasket. The gasket between the Briggs & Stratton engine block and crankcase cover is a made of a thin waterproof paper that fits the engine block shape and has holes for the crankcase bolts to go through.
Unscrew the oil drain plug on the side of the Briggs & Stratton engine block or on the base of the engine with the proper sized wrench. Allow all the oil to drain out into the oil drain pan.
Flip the Briggs & Stratton engine upside down so the crankshaft is facing up. Unscrew all the bolts on the base of the crankcase cover with the proper sized socket wrenches. Pull the cover off.
Peel the old crankcase gasket off. Wipe around the edge of the engine block and crankcase cover with a dry rag to remove any excess oil or debris.
Place the new crankcase gasket against the engine block. Line it up correctly over the bolt holes that the crankcase attaches through.
Slide the crankcase cover back on. Snug up all the bolts. Put the correct sized socket on the ft-lb torque wrench. Tighten a bolt to 15 ft-lb, then tighten a bolt on the opposite side of the crankcase to 15 ft-lb; continue this opposite tightening to properly seal the gasket in place.
Flip the engine right side up again. Add the correct amount of oil to the engine.