I've been on both ends of this highway, but never have actually traveled it. For the record, it connects to the 20 just before Philomath...not in Corvallis. I have seen large logging trucks pulling off of 34 at the 20, so I would suspect that a motor home would not have any problems.
Hopefully, someone who has actually traveled this route can chime in.
Ron, Sandie, and Maggie May
2013 Tiffin Phaeton 42LH
2011 GMC Terrain SLT-2