Man, Harley-Davidsons. Fuck Harleys. Harley engines are a 1990s tweak of a 1970s update of a 1930s engine built by people who learned engine design from 1910s farm machinery.

Not that there’s nothing to be said for that. A modern Harley mounts the most reliable 1930s engine in history, and when it fails it fails in very well-documented ways.

Mazda for a long time made cars with Wankel rotary engines (1960s, y'all) which were a significant step up from piston engines, but no one had a goddamned clue how to maintain them.

And I mean hell, before that we spent a few thousand years mastering the ox and horse.

What we really need is another world war to legacy us with a decent knowledge base on turbine engines.