I've ridden most of the back roads in Oregon as a passenger in Logging Trucks. My family are all in the logging industry out of Myrtle Creek & Myrtle Point area, I'm the only one who escaped. The Cascades in Oregon and the coastal range are some the the most beautiful scenery that I have ever come across. The rivers should be down quite a bit this time of year so there should be some great swimming holes along that route.
Most of the roads are not fit for a cruiser but if your on a dual sport bike it should be no problem. Watch out for log trucks, they won't be watching out for you. Many times they will cut a corner tight in order to make the trip faster. At times the roads are pretty desolate and if you have problems you could be there overnight before anyone comes along. Take extra gear to keep warm just in case and some emergency food.
Another great run is the Old McKenzie Highway out to Sisters.
Enjoy the ride.
PS, I called my PBFH Sister in Law off so your safe