Just got back from the UP. All you need is an ORV sticker from the local gas stations (got mine from the Holiday station in Iron Mountain) and you can ride the ORV trails in Michigan. Sticker is good until year's end, I think they are around $16-17 each.
Ride Bass Lake, it's 26+ mile of great singletrack, or for something tighter, but still fun, the 27 mile Moss Lake loop. There are lots of good trails in Michigan, just google for the ORV trail website and there you can get locations, trail maps and be good to go.