KNUCKLEHEAD DON
A knucklehead is someone who is stupid, a dunce or an idiot and always does or says something totally foolish.
Knucklehead is an informal term that comes across as insulting, depending on how we use it. The former guy is one.
Riders nicknamed the engine the "Knucklehead" because of the distinctive shape of the polished alloy rocker boxes atop each cylinder. The Knucklehead provided vastly increased horsepower and durability and became the bedrock of Harley-Davidson engine design for the next 65 years.