The most common bike we saw on our way to Khanjerab was CD70, dozens and dozens of them. One of them was carrying 3 people towards the Babusar Pass.
The horizontal Honda engine designed in the 60s is a legend. It is a fabulous bike and totally reliable, more than many bigger ones. I know it because I took one to Chitral and Shandoor in 1982.
I know of a retired Col who travelled to all these places in his Honda Cub 50.
It is not the displacement of the engine but the rider that really matters.