Washington Hwy. 129 - Oregon Hwy 3

WA-129/OR-3 is steep and with many hairpin curves well before and after crossing the state line. I would never tow it. Extremely scenic though. An awesome day trip.

Thank you! You have confirmed what was my concerns.
We will get to Wallowa via a different route.

I have taken our small trailer via that route. Fields Spring State Park at the top of the Rattlesnake Grade just on the WA side is a nice stop or layover. The Rattlesnake Grade bear the state line is scenic and historical, but its steepness and sharp curves are true to the name. Here is a blog (not mine) that describes the route well:
http://destinations-northwest.blogspot.com/2012/04/rattlesnake-grade-road-to-remember.html?m=1

Drove it years ago in a small truck. Not a road I would suggest if your in a hurry. Youtube has several clips from a motorcycles prospective you might want to watch before deciding.