I did that road on my BMW Cruiser. That was when I decided to get the bike that actually suited my riding. The bike withstood the punishment, although, I went around 5 - 10 kph most of the time. I did get some interesting looks from the locals as I went by.That road from Princeton over to Summerland can be a chore. We did it, two-up on a 400 Maxim, loaded down with camping gear one summer and rattled every cable off that bike. Washboard city. Lots of silt, too.
Big smiles by the end, though, but that might have been from the showers at the campground. That was the year of the big Kelowna forest fires, and we camped across the lake and watched them burn. Strange to say, but it was quite beatiful.