How do you replace push rod in a lawn mower?

Most lawn mowers do not use a push rod to open and close the valves as the end of the valve stem sits directly on a cam. The cam of the camshaft opens and closes the intake and exhaust valves. This is called an Overhead Valve or OHV.

IF a large, old engine does use push rods, apply the same methods as used in an auto or motorcycle engine,: Namely, remove the valve cover and then the valve train. Each valve has a push rod in an opening underneath each valve rockerarm.