I'm biased because I'm a geologist, but I would bypass Montana and go straight from Sturgis to Yellowstone/Tetons. Try and book a cabin at Roosevelt Cabins
http://www.usparklodging.com/yellows...gn=Yellowstone. Plus, you should see at least one National Park in Utah. I recommend Arches NP, then off to Cortez, CO and do a loop up to Telluride, Ouray, and down to Durango. Then ride to Denver and ship your bike home.