The top speed of a 125cc dirt bike can vary depending on various factors, including the specific model, engine configuration, rider weight, terrain conditions, and modifications. However, it's important to note that 125cc dirt bikes are generally designed for off-road riding and may not prioritize top speed as much as other factors such as acceleration, maneuverability, and durability.
That being said, some 125cc dirt bikes are known for their relatively higher top speeds compared to others. One example is the Yamaha YZ125, which is often praised for its performance and top speed in the 125cc category. The exact top speed can vary based on factors mentioned earlier, but the YZ125 has been known to reach speeds around 70-75 mph (113-121 km/h) in stock form.
It's worth mentioning that achieving the maximum top speed on a dirt bike may not always be safe or advisable, as it depends on the terrain, riding conditions, and rider experience. Safety should always be a priority, and it's essential to ride within your skill level and the limitations of the bike.