Harley-Davidson’s Evolution engine — frequently referred to by riders as an “Evo” or “Blockhead” engine — fueled increases in Harley-Davidson’s overall sales and stock price for over 20 years after it first entered the motorcycle market in 1984. The small Evolution engine permanently replaced the Ironhead engine, and as of November 2010, is still being produced by the Harley-Davidson motorcycle company. It can be found in Harley-Davidson’s 883, 1100 and 1200 XLH Sportster models.
The larger Evolution engine, however, was replaced by the Twin Cam 88 engine in 1999. Before production of the big Evolution engine ceased, it was commonly found in dozens of Harley-Davidson’s 1340 displacement models over the years — most notably the Softail Springer 1340.
The 883, 1100, and 1200 Evolution engines are each small V-twin, four-stroke engines. The 1340 Evolution engine is a big V-twin, four-stroke engine.
The 883 Evolution engine has a displacement of 883 cubic centimeters (CC), the 1100 has a displacement of 1,101 CC, the 1200 has a displacement of 1,200 CC, and the 1340 has a displacement of 1,337 CC.
The Evolution engines on the 883, 1100, and 1200 models each have a compression ratio of 9:1. The Evolution engine on the 1340 model has a compression ratio of 8.5:1.
The 883 Evolution engine has a maximum horsepower (HP) of 46 at 6,000 rotations per minute (RPM), and can reach a top speed of 92.6 miles per hour (MPH). The 1100 Evolution engine has a predictably higher maximum HP of 50 at 5,500 RPM, with a top speed of 101.9 MPH. The 1200 Evolution engine has a maximum HP of 58 at 5,300 RPM, which is considerably higher than the abovementioned motorcycles. The larger 1340 Evolution engine has a maximum HP of 58 at 5,000 RPM and a top speed of 102.5 MPH.
Bore and Stoke
The Evolution engine on Harley’s 883 models has a bore of 3 inches and a stoke of 3.8 inches. The Evolution engine on Harley’s 1100 models has a larger bore — at 3.4 inches — and the same 3.8-inch stoke. The Evolution engine on Harley’s 1200 models has a bore of 3.5 inches and a stoke of 3.8 inches. The Evolution engine on Harley’s 1340 models has a bore measuring 3.5 inches and a stoke measuring 4.3 inches.
Fuel Control and Cooling
All Evolution engines — regardless of model — have two valves per cylinder, overhead valve fuel control, and an air-cooling system.