I haven't been up to Alaska, but in '06 Mike and I rode up from Ohio into Canada and across on that same route to Vancouver BC. I was still on two wheels at the time with my Fat Boy. Man, what a wonderful trip!!!!!! Through the prairies, expect long stretches without seeing another living soul (and you can lock on the gas and fly for miles --- we did a couple of 600 mile+ days as a result). Those long stretches also mean that you should definitely not push your gas tank, but fill up when you see a station! My dad was born and raised in Manitoba, and FORTUNATELY we were near his home town. We were literally running on fumes, I think, but an old farmer who grew up with Dad gave us coffee and reminisced while his grandson filled up our tanks from his personal supply, as we still had miles to go before a real town that actually had a gas station!
On a side note, that was the best stop we made as he hooked me up with a number of Dad's old buddies who took me to the abandoned farmhouse where Dad was born, gave me apples from trees my grandfather planted, and told me stories that would have embarrassed Dad no end if he were alive to hear them now . I loved it!
If you know ahead when you might reach Banff and Jasper area, call ahead and reserve a room. We made the mistake of thinking we could "wing it", and every place was booked up.
We therefore had a much shorter visit in that area, snapped a few pictures, and had to ride a couple more hours to finally find a vacancy! We had hoped to spend the night there and take the next day to ride around the park and view more of the glaciers, etc., but we had to go so much further that it meant we missed out on that opportunity.
If you do head down to Vancouver before going north to Alaska, be sure to take the Fraser Canyon highway south out of Kamloops (my Mom's birthplace) instead of the newer freeway. It is a bit slower, but only a bit; and the views are amazing. If you have time take the cable car down into Hell's Gate along there --- a great experience!