The ideal top speed for a 250cc motorcycle can vary depending on various factors such as the bike's design, engine performance, aerodynamics, and other factors. Generally speaking, most 250cc motorcycles have a top speed in the range of 70 to 90 miles per hour (112 to 145 kilometers per hour). However, it's important to note that these figures are approximate and can vary between different motorcycle models. Additionally, factors like rider weight, road conditions, and wind resistance can affect the top speed achieved by a motorcycle.