Many many years ago I hitchhiked to Alaska on the Alcan Highway.  At the time, it was mostly 2-lane gravel, and folks had hardware-cloth rock screens in front of their windshileds and radiators.  Everyone carried 2 spare tires and two gerry cans of gas.  I remember meeting a kid in Anchorage who rode a Honda 360 all the way from Montana.  He was still driving it around town.  I said to him, "You must love that bike."  His simple response was "I hate it man, I HATE it."

That trip is on my bucket list javascript:void(0)

I've driven up/down the alcan a number of times.

A couple of things:
1) The only gravel left is areas of road construction (perhaps 5-10 miles at a stretch)
2) You need to have at least 200 miles of range. Some of the mom/pop gas stations have closed (or severely reduced hours), so you need to plan your fuel ups.
3) Get the latest Milepost magazine
4) If tent camping:
    The provincal parks in Canada are usually very nice.
    Some campgrounds will advise against tent camping starting in june (bears).
5) Plan for about 600 miles a day (although 800/day is also feasible if you have an iron butt)
6) Carry an air hour to clear buffalo from the road (barking dog though is actually better).