A general purpose air-cooled, four-cycle engine in which a first ball bearing supporting the output shaft of the crankshaft is larger than the second ball supporting the other end of the crankshaft, and the first bearing has an external diameter which is approximately equal to or greater than the distance from the crankshaft to the camshaft. The camshaft driven by the crankshaft is supported by sliding bearings. The governor which controls the rotation of the engine and which is driven by the rotation of the crankshaft is enclosed in the crankcase on the same end as the cooling fan, which is the end opposite the output end of the crankshaft. This invention fulfills the demand for a smaller crankcase; does not make use of special bearings; and achieves a greater bearing capacity through the use of large-diameter standard-precision ball bearings. In addition, it simplifies the required processing and allows the assembly process to be automated.