The process of replacing primer bulbs on mower engines varies slightly from manufacturer to manufacturer. The Briggs and Stratton engine uses a retainer ring to secure the primer bulb to the engine crankcase. The most common reason for primer bulbs to become faulty is due to leaving gasoline in the engine when storing the mower in the off season. This contributes to making the bulb brittle and causing cracks. You can purchase replacement primer bulbs at home improvement centers and Briggs and Stratton dealers.
Place your lawn mower on a level surface and disconnect the spark plug wire from the top of the spark plug. Grab the plug wire where it connects to the spark plug and pull the wire off with your fingers.
Remove the screw that secures the air cleaner housing to the mower with a flat-head screwdriver. The air cleaner housing is the rectangular box that sits above the primer bulb.
Remove the plastic ring cap that covers the primer bulb retainer ring. The cap will pull straight off with your fingers.
Locate the notches on each side of the primer bulb housing. Insert a flat-head screwdriver into each notch to press the retainer ring open. Pull the retainer ring and the primer bulb out of the housing.
Set the new primer bulb into the housing and place the retainer ring over the primer bulb. Grab a socket that is slightly smaller than the outside diameter of the primer bulb. Place the open part of the socket over the retainer ring and tap the socket with a hammer to seat the retainer ring.
Place the plastic retainer cover over the retainer and primer bulb. Set the air cleaner back into position and secure with the retaining screw. Push the spark plug wire over the top of the spark plug until the wire snaps into place.