The top speed of a Honda 400EX ATV (All-Terrain Vehicle) can vary depending on factors such as rider weight, terrain, and modifications. However, the Honda TRX400EX, which is powered by a 397cc four-stroke engine, typically has a top speed ranging from 65 to 70 miles per hour (105 to 113 kilometers per hour) in stock form. This speed can be influenced by various factors, including riding conditions and equipment setup.
It's important to note that riding at high speeds on an ATV requires skill, experience, and caution. Always adhere to local laws, follow safe riding practices, and wear appropriate safety gear, such as a helmet and protective clothing. Additionally, modifications to the ATV's engine or other components can affect its top speed and performance.