No, not every motorcycle has its engine on the side. The location of the engine can vary depending on the motorcycle's design and configuration. The majority of motorcycles have their engines located between the two wheels, either in a longitudinal (front to back) or transverse (side to side) orientation.
In most motorcycles, the engine is positioned in a way that the cylinders are aligned parallel to the frame of the motorcycle. This arrangement is commonly referred to as an inline engine or an inline cylinder configuration. However, there are other engine configurations as well, such as V-twin, V4, flat-twin, and boxer engines, where the cylinders are arranged in different ways. These engines can be positioned with their crankcases facing either side of the motorcycle.
It's worth noting that there are also motorcycles with unconventional designs where the engine may be placed in different locations. For example, some electric motorcycles have their motors integrated into the wheel hubs, while others have the motor positioned centrally within the frame for better weight distribution.
Overall, the placement of the motorcycle's engine can vary depending on factors such as the manufacturer, motorcycle type, design goals, and engine configuration.