A barrel engine has a longitudinal output shaft defining a longitudinal axis. A plurality of cylinders is disposed about the output shaft and are each generally parallel to the longitudinal axis. A cam plane is defined perpendicular to the longitudinal axis and disposed between the open ends of the cylinders and a second end of the engine housing. A cam plate is disposed in the engine housing and supported for rotation about the longitudinal axis. The cam plate has a central portion and an outwardly extending cam portion. The cam portion has a cam surface that undulates from one side of the cam plane to the other. A flywheel has a plurality of lobes, each lobe being disposed generally in alignment with an area where the cam surface undulates closest to the open end of a cylinder.