Once at the station, do not get on the dirt bike. Instead, enable the "Spawn Jetpack" code, then kill the men on the train with the shotgun. Once you have killed the men on the train, you must go back to Smoke and get on the dirt bike to pass the mission. Additionally, smoke has very bad aim. Try to keep up speed with the train. When Smoke tells too take the hill, do not, as this makes completing the mission almost impossible. Instead, stay with the moving train. Go past the barrier and try to avoid getting hit by the other train. Also, turn off the vibration option on the controller to help keep your hands steady while on the tracks.