# digressionAll of the Japanese motorcycles that I'm familiar with, both air and water cooled, use the cam in plain aluminum bore construction. Those are some high revving engines and many of them, like GoldWings, are ridden many miles.
That's true of most non-competition four strokes, especially on bikes from the 80s and older. Modern race-oriented engines typically come with bearings for cam journals (whether Japanese or European). KTM started using cam bearings in their 90's era LC4 engines, which were also utilized in their non-competition dual sport lineup:
# end digression