Understood.
Since you are going to come back through Bend, a more scenic route to Portland would be up the Columbia River Gorge Scenic area
You can travel Freeway on the Southside or cross the river and travel a much prettier route on the north side in Washington State.
From John Day to Portland, taking the Gorge route is same miles and same time as Hwy 26 for just traveling through.
Try this for an example although it does a little detouring.
https://goo.gl/maps/LHi8V
The pic I attached below is entering Columbia River Gorge heading west on I-84. You can just make out Hwy 14 on the Washington side across the water there. Much better ride on a Motorcycle...
I can probably get more specific if you want it.
Trying to show some good things to see.
Forgot to mention, this is Motorcycle/Farm Country That time of year you are likely to find or join up with many motorcycles riding around.
All the businesses through there cater to Motorcycle/Bicycle riders. They are very friendly.
Do be on the lookout for wildlife, especially in the Deer thirty windows. Typically daybreak until about 9am and late evening from about 5:30 to dark. Lots of animals are moving for water and food at those times.