Ironhead Sportster

When the first Sportsters rolled out of the Harley-Davidson factory in 1957, they were powered by the iconic ‘ironhead’ motor—which would remain in production until 1985.

The Sportster is still in production 60 years later, and the ironhead has the longest production history of any Sportster engine. In the early days, the 55ci motor offered a lot of bang for the buck, with a 7.5:1 compression ratio, a 90-degree valve angle and four cams.

In 1972, capacity was bumped up to 61ci and the compression ratio to 9:1. The extra power took the Ironhead Sportster to a heady 110 mph.

Today, there are tens of thousands of Ironhead Sportsters still on the road, and a huge aftermarket parts industry has sprung up around the engine. That makes it easy to build, tune and maintain—and the ideal platform for both budding and experienced custom builders.