The compression ratio of Harley-Davidson motorcycles can vary depending on the specific model and engine configuration. Different models and engines within the Harley-Davidson lineup may have different compression ratios to suit their intended purposes and performance characteristics.
Historically, many Harley-Davidson Big Twin engines, such as the Evolution (Evo) and Twin Cam engines, had compression ratios in the range of 8.5:1 to 9.5:1. These engines are designed to deliver strong low-end torque and a smooth power delivery.
In recent years, Harley-Davidson has introduced the Milwaukee-Eight engine, which is their latest generation V-twin engine. The compression ratio for the Milwaukee-Eight engine can vary depending on the specific model and displacement. For example, the Milwaukee-Eight 107 engine has a compression ratio of approximately 10.0:1, while the Milwaukee-Eight 114 engine has a slightly higher compression ratio of around 10.5:1.
It's important to note that the compression ratio is just one factor that affects engine performance and characteristics. Other factors such as engine tuning, fueling, exhaust system, and overall design also play a significant role. The specific compression ratio for a particular Harley-Davidson motorcycle can be found in the technical specifications provided by the manufacturer for each model and engine variant.