It's a reference to R. Crumb's "Zap Comix". The Hog Ridin' Fools were regulars in those.
The national president of the Devil's Disciples M.C. lived in my home town. They were and are a nasty bunch, but they're back in their stomping grounds in the S.W. US these days. I was friends with his youngest brother when they turned up in '70. They all rode those stretched frame Harley's with the ape-hanger handlebars. One of 'em wore a spiked Prussian helmet. It was like a bad biker movie.
I was about the same age you were then. All the kids in town though my friend and I were cool because we were always over there, and all the parents thought we were on the direct road to Hell. The only reason we went there because there were always loaded girls running around half naked. What boy going through puberty is going to pass on that?