Good Morning Rick, I've been kicking around riding parts of the TAT. As you may or may not know, my younger brother passed away in 2016 from ALS and I've been thinking of doing a ride/fundraiser for ALS while riding the TAT. My issue is I cannot be away from a month or so. I haven't really figured that part out yet. Lets talk soon....
A 650 or smaller bike is a wise mount for the TAT. Step through Honda's have made the journey and so have 1200+cc bikes. Depending on how you travel/pack you can easily add 100-250 lbs to the weight of the bike and that weight adds up after a while.
Once you hit Colorado and beyond; less is more. Your mileage may vary.
Rick my Son is thinking about a Yamaha 700 tenere. If he gets one I will give You the good & bad. My pal has a new 790 KTM & he loves it. Both are very experienced & very good riders.Please keep us informed of your plan. If I can help out when you get near Commiefornia I would be Happy To. Happy Trails!
Rick I was reminded that I was the support vehicle for my Son on the T. A. T. thru Oregan & No. Calif. Good times ! He has more experiance with Adv. touring than anyone I know. When you want he said he can pass on things he learnded the hard way. He is envious of your plan.