Back then, street bikes still retained some vestige of off-road capability from the days when there were still many roads that were not paved. People EXPECTED that their street bike could be ridden down fairly rough dirt roads without much thought. I doubt that Goldwing owners think that way now. Two of the preeminent bikes at this were the BSA and Triumph "scramblers." They were called "scramblers" because they were usually fitted with high pipes and slightly more aggressive tires in case you intended to compete in scrambles races, the precursor to motocross. The modern AMA Grand National off-road series is, I think, the grand child of the old scrambles races. Click here to see my comments on riding a classic Rickman Triumph a dfew years ago.
A Triumph ISDT bike, a waxed cotton Belstaff jacket, open face helmet and Uvex glasses and goggles. You don't get more manly than this. It was all real at the International Six Days Trials 40 years ago. McQueen was no poser.
picture borrowed from http://www.triumphrat.net who probably got it somewhere else.