Of the ~735km . . . > 700 are gravel.
It's rideable on that fat-tired Harely IF it's dry. Rain tends to bring out the clay and that get's REALLY greasy. The road is a marvel in the way it winds through the sub-Arctic so beautifully but there are a number of places where washouts occur and delays can be a few hours or days though multi-day delays are rare.
You'll need to make it to Eagle Plains from "the bottom" for gas - ~350km.
Highly recommended and massively over the "haul road" (Dalton Hwy) to Prudhoe Bay. Did it in '93 on a K75s (lots of rain), did it in 2010 on a KTM ADV (dry and rain, didn't matter much to the KTM).
Orange, it's the new black.