Over its 120-year history, Harley-Davidson, based in Milwaukee, Wisconsin, has firmly established itself as the leading name in American motorcycles. The brand has achieved this by launching a series of iconic bikes, known for their rugged style and unparalleled power, which few competitors in the motorcycle industry can match.
With over a century of innovation under its belt, Harley-Davidson continually strives to enhance the power and performance of its motorcycles. In 2020, the company arguably surpassed its own standards with the introduction of the Screamin' Eagle Milwaukee-Eight 131 Crate Engine. This engine was touted as the highest displacement engine Harley-Davidson had ever produced at the time, until the release of a 135-cubic inch crate engine for newer models in 2023. Despite the hefty price tag, which approaches the cost of a new bike, the 131 Crate Engine has become a coveted upgrade for those seeking maximum power.
There are three versions of the 131 Crate Engine: two designed for 2017 or later Touring models—one Twin-Cooled and one Oil-Cooled—and another Oil-Cooled version for select 2018 and later Softail bikes. However, not all Harley-Davidson models that fall within these categories are compatible with the 131 upgrade, so it's essential to research whether your bike can accommodate it. Additionally, Harley-Davidson requires ECM calibration with the Screamin' Eagle Pro Street Tuner or a dealership-installed Screamin' Eagle calibration for these upgrades, and even then, they aren't legal in all 50 U.S. states.
The Screamin' Eagle Milwaukee-Eight 131 Crate Engine is street legal in 49 states, with California being the exception due to its strict vehicle emissions standards. The engine's massive power output is partly why it’s restricted; as noted in a 2020 Cycle World review, the 131 Crate Engine essentially turns your Harley into a hot rod, delivering 121 horsepower and accelerating from 0 to 100 in just over 9 seconds—power that the average rider might struggle to handle safely.
If you're wondering which Twin-Cooled Touring models can be equipped with the 131 Crate Engine, it is compatible with a variety of 2017 and later bikes, including several CVO models, Road Glide Ultras, Road Glide Limiteds, Ultra Limiteds, Ultra Limited Lows, and the 2023 Electra Glide Highway King. For Oil-Cooled Touring bikes, the 131 fits many Road Glides, Street Glides, Road Kings, and Electra Glides, including some CVO variants.
As for the Softail models compatible with the Oil-Cooled 131, the list is extensive, covering several Fat Boys, Street Bobs, Low Riders, and Sport Glides, among many others. If you're unsure about your bike's compatibility with the 131 Crate Engine, it's best to consult your local Harley-Davidson dealer for advice. Keep in mind that the 131 Crate Engine is only considered street legal when installed on a compatible Harley-Davidson model and after the necessary emissions upgrades have been completed.