Denver to Detroit, and back

[blackjackdavey]

i want to plan a trip for sometime this summer, maybe July or August from Denver to Detroit, then back a week or two later. I-80 is the straight shot but not fun on KLR which is what i have. also i know 2 days would be hard, but i don't want to take more than 3 days.

http://goo.gl/maps/UDt7b

looks like US-36 will get me to Illinois, not sure if it will be much fun, but its an option. Can anyone suggest segments to hit up on the way that wouldn't put me out of the 3 day limit? some dirt or fun unpaved roads could be good to try on the way.

web-cross-posted to KLR forum
thanks