I've used Kenda 761 for long road miles and good gravel roads. Inexpensive. I might choose Duro 904 for a trip like that.
I really enjoy long miles on my KLR, and the second generation KLR should be more suitable for long miles than my first gen. I'd suggest riding every chance you get plus a couple of long days. For those long days I'd say take a break any time you want one; if it works for you then the breaks will naturally get farther apart.
Did I miss your starting point? Using the middle of the state I get two 700 mile days. I would DEFINATELY mix 2-lane and freeway. The freeway gets miles down quickly but can wear me down and isn't all that interesting. Two lane roads are more interesting and the people* are more interested in the passersby. People along the freeway learn to not care. Small roads can be almost as fast as freeways but there's more navigating unless you're on a 2-lane equivalent of a freeway (I don't know south, but in the north these are US 2 and Canada 17). Small roads may take longer but I arrive fresher. I've done several 1,025+ mile days on my KLR, but back-to-back 700-mile days are barely easier than one 1,000-mile day.
I'd also recommend a hydration bag in a tank bag. I use Platypus "hosers". The bike can carry the weight.
With prep your trip can be enjoyable. Starting without building tolerance may be a test of endurance instead of a fun, long ride.
* People I meet when riding solo are usually great -- waitresses**, cashiers, campground/motel staff, and just the people at the next table in a restaurant. They often have great stories to tell and will often talk to the guy on what looks like a dirt bike with far-away state plates.
** Old curmudgeon sexist statement. But really, stop in any locally-owned independent diner and the "wait staff" will be 99.5% female.
Thanks for all the advice.
As for tires, I'm thinking I may go with some 60/40 tires, like the duro 904. But, the price if those shinko 244 is really tempting, and my local shop carries shinko. What about the shinko 700 for a 60/40 tire? I looked them up on here but didn't find much helpful info.
I'll have to wait another week to do a long ride... I've got my class next weekend to get my license so that I'm legal. I work out in the middle of nowhere, so I've just been riding to work occassiknally. This is the first bike I've owned. So then we'll see how long I can stand to ride in a day. I mainly want to rip through the Midwest and plains as fast as I can stand in order to get to Utah. I'm mainly a runner/hiker and secondarily a moto rider. But I certainly can't wait to get out on some of those backcountry roads to see what I can/can't do on the bike!
I have a couple other questions as far as how I'll be packing the essentials. I don't have much interest at the moment in buying and installing all kinds of luggage racks, hard cases, etc. Primarily because I spent large amounts of money on running shoes and races, and the other reason being that I feel that it just promotes me packing more unnecessary items adding more weight. I really like the minimalistic, unencumbered feel of the bike, and I want to keep it that way.
With that said, here's the plan. I'm going to put on a 16 tooth sprocket to help out with mileage and possible oil burning, I've got the tall Dakar windscreen but haven't yet installed it, I will be putting on a 12v outlet (maybe), I have a wolfman enduro tank bag, and for ALL of my other belongings like clothes and running/hiking gear I'll be strapping my 65L osprey pack to the back end of my seat and top rack with the can type straps.
As for riding through possible rain, I haven't came up with a great solution other than wrapping my osprey pack in my tent's waterproof footprint, and wearing my running rain gear (I don't have any riding clothing gear other than helmet and don't plan on getting any).
I'll be using your advice for the platypus hosier water reservoir, cause I already have one if those and that's a great idea!!
I haven't figured out what to do about extra gasoline, since I have no luggage racks other than the top rack that my pack will be sitting on. Maybe just get a bombproof gas can and strap it to the top of my pack?
I was worried about the weather being too hot out in Utah, but the average high for July temps near Monticello is about 85f!! That's cooler than southern Illinois and with the lack of humidity that we have here, it'll feel like spring!