No, 125cc and 250cc motorcycles typically do not have the same engine. The engine size (displacement) is a measurement of the engine's total volume swept by all of its pistons. A higher displacement generally indicates a larger and more powerful engine.
While both 125cc and 250cc motorcycles fall into the category of small displacement motorcycles, they usually have different engines. The engine design, configuration, and specifications can vary significantly between different motorcycle models and manufacturers.
A 125cc motorcycle typically has a smaller engine with a single-cylinder configuration, whereas a 250cc motorcycle can have a single-cylinder or a twin-cylinder configuration. The specific design, materials, and performance characteristics of the engines will depend on the manufacturer and the intended purpose of the motorcycle.
It's important to note that engine size alone does not determine the performance or capabilities of a motorcycle. Factors such as engine design, tuning, weight, and overall motorcycle dynamics also play a significant role in the performance and handling characteristics of the bike.