Grant and I walked into the remote and seldom (like, I have heard of one party to paddle it in the past 30 years) visited Tyers river in the South East Yukon. They spoke of portages, canyons and epics.
Access is off the CanTung road via old mining roads and animal trails.
The Tyers flows into Frances lake, and to make the loop, you then paddle down the Frances river to the bridge on the CanTung road. The Frances has its own fun with a BIG water class III canyon just below the Tuchitua river. Watch for monster holes and waves!
We found fantastic white water, canyons galore (all runnable) and beautiful country. At least it seemed to be, what we could see of it given that it poured rain and the river was flooding.
A classic that should be be on your Yukon hit list, given its easy one day walk-in access and quality white water.
Packrafting the Tyers River from Yukon Frolics on Vimeo.