The top speed of a 2006 Kawasaki KX125 dirt bike can vary depending on various factors such as rider weight, riding conditions, and modifications made to the bike. However, the average top speed of a stock 2006 Kawasaki KX125 dirt bike is approximately 70-75 miles per hour (112-120 kilometers per hour). It's important to note that these speeds are approximate and can be influenced by several variables. Additionally, modifying the bike or adjusting the gearing can potentially increase its top speed.