The maximum speed of a bike with a 125cc engine can vary depending on various factors, including the bike's design, weight, aerodynamics, gearing, and other performance characteristics. Generally, most 125cc motorcycles have a top speed in the range of 55 to 70 miles per hour (88 to 113 kilometers per hour).
Keep in mind that these figures are approximate and can differ based on the specific model and manufacturer. Additionally, external factors such as road conditions, rider weight, and wind resistance can also influence the actual top speed achieved by a motorcycle.
It's important to adhere to speed limits and local traffic laws while operating any vehicle, including motorcycles, to ensure safety for yourself and others on the road.