I am throwing down the gauntlet. I've been researching and compiling a Great Western adventure. The last one was Mantua to Layton on the worst of possible game trails (see link on sidebar). This new version starts from Salt Lake City and heads into the mountains on single track trails, ATV paths, four-wheel drive roads, and gravel roads, all the way to Boulder, Utah. The route should take 4-5 days with two resupply points.
The first leg of the tour goes through the northern Wasatch via Mill Creek canyon to the Crest, over Brighton and down into Provo Canyon, back up to the southern Wasatch at Vivian Park through motorcycle paths. Camp somewhere in the mountains and head over a pass and down on forest service roads to cross highway 6 at Trucker, Utah (ghost town), and then south on the famous Skyline Drive (see below Google Earth image).
Ride the Skyline drive till you want to camp somewhere, and ride it the next day for about 100 miles, till you meet the fork for the Great Western Trail ATV (GWT) route. Take the route down a huge elevation drop till you run into I-70 and ride about 10 downhill till you are out of the mountains to the town of Salina, Utah. At Salina get a motel, buy a whole pie for yourself at Mom's Cafe, and watch crappy cable TV for as many days as your legs need. When you are ready, head back into the mountains via the I-70 frontage road till you meet back up with the GWT. Head south east on the GWT ATV trail network for 80 miles or so till you roll into Teasdale, Utah. Rest. Go south of Teasdale on 4wd roads up Boulder mountain to Donkey Reservoir and take various forest service roads and trails that rim Boulder mountain till you drop down onto the highway 12 and ride it out a few miles to the Hell's Backbone Grill in time for dinner.
There are a few mystery sections that sources say there is a trail/road there, but I could not spot it on Google earth. And there looks like there are two passes that may include some helacious cross country bushwhacking for a mile or so. More research needs to be done. I have already ridden about 1/4 to 1/3 of the route, and for some of the other places I have a good sense that they are going to be great riding. From Boulder, one could easily ride on Hell's Backbone road all the way to Escalante, and from there keep going on the recently devised Trans Utah Escalante to St. George route listed on bikepacking.net and the brainchild some St. George riders at 2-epic.com.