The Iron Horse trail has sectons of heavy, loose gravel, you might want to check it out. Could cause a dirt bike some control problems. Try one of the St Paul qaud/bike dealerships.
Rode from St Paul to Heinsburg and back a couple of years ago. Nice trail, easy ride. Will go back again soon. Nice place to have a snack a few miles east of St Paul by a pond. Take your time and enjoy the ride. I would go in the summer or early fall for the color.
Thanks to Gary & Kim for hosting the ride and helping us out. We enjoyed it and will be back next year if you go again. I'am already working on some others to come out and enjoy the area and fellowship.