I know there are dedicated bike trails around the Black River Falls, Rock Dam, Hatfield, etc. area. I may be wrong, but I think bikes can ride the ATV trails there too, but not vica-versa. I know for sure that ATVs can't be on the bike trails.
There is also bike legal trails in the southern section of the state. From Monroe to Mineral Point and Belmont. This is pretty boring though as it's just old railroad grade. I'm sure there are other areas. but these are the ones I'm familiar with.
In Wisconsin you register bikes for trail use just like a quad. Click here
https://jc.activeoutdoorsolutions.com/wihf_...s/app/goHome.doDoesn't matter 2 or 4 stroke, just as long as the exhaust is spark arrested & Forestry legal.