Spokie -

I've toured solo up to Alaska, the Yukon, and the Northwest Territories a half dozen times - although not in the past three years. (Why you have that qualifier - and not your own parameters is baffling.)

It seems that you have only the faintest idea of the geography and roads since you say "to the Yukon and Ketchikan" when a person heading north from Washington would first get to Ketch - THEN continue on to the Yukon. One piece of advice if you plan to solo - - you had better know where you are going. And know the climate.

You do not indicate whether you will do a grand loop or bike one way. Roadwise, there are two basic options north of the Yellowhead Highway - - the Alaska Highway and the Stuart-Cassiar. These meet at Watson Lake, YT. You have another option in the Yukon via Dawson City or Kluane. These meet at Tok, AK. Then you can opt for Fairbanks or head southwest towards Anchorage/Valdez.

Many people choose to use the Alaska Marine Highway as part of the trip. The ride from Skagway/Haines into the interior is steep, remote, and beautiful. Also, an option is to ride up Vancouver Island to Port Hardy then take the BS Ferry to Prince Rupert. This is a popular option for those doing the Stuart-Cassiar.

Bells Alaska Guide online has detailed mile by mile logs for all of these highways.
It's not a good idea for a beginning tourer - but possible.
PROVIDED you are prepared and careful.
ABSOLUTELY KNOW BEAR PRECAUTIONS.