Also plan your trip so that you can have parts shipped to you. This requires someone some where that will be your support crew. If you ruin a wheel in some places, your best bet will be finding a used bicycle with that type of wheel, because overnight shipping would be more expensive. On the other hand, you need to know the location of every bicycle store on the route, if you need a tire, you need to be able to find the closest.
You will be crossing the Continental Divide, on a motorized bicycle you will probably have problems with your carburetor. Better know how to tune the jets.
Flats, expect lots of flats, my brother and I made an 80 mile trip back in 1959, it seemed like we had to buy extra flat repair kits in almost every town we went through.
With a 4 stroke, you will need to change the oil, and change it often. I would make up an oil changing kit make that job as simple as possible. Lawnmowers call for an oil change every 40 or so hours. Not sure on you motor choice. Also check on air filter maintenance, probably going to need that done as routine maintenance.
One way to plan the trip is to run the Google map using a bicycle as the mode of transportation. Then search for bicycle blogs that bicyclists have written about area that you will be traveling. The writers of the blogs have been down those roads and will give some better descriptions of what to expect. The blog writers information will become your best source of reliable info.
Another source of info is George Wyman, he made the first trip across the states on a motorcycle, a converted bicycle. This memorial page is an interesting read.
http://wymanmemorialproject.blogspot.com/p/project-goals.html