You May Not Want A Used Harley-Davidson With This Engine (For A Number Of Reasons)

Harley-Davidson’s Milwaukee-Eight Engine: A Cautionary Tale for Used Motorcycle Buyers

Harley-Davidson motorcycles are more than just vehicles; they are rolling pieces of American history, known for their distinctive growl and unmistakable presence on the road. Among the many elements that make Harley-Davidson iconic, its V-twin engines stand out, particularly for their signature “potato-potato” exhaust note that has become synonymous with the brand. However, even legends can have their flaws, and the Milwaukee-Eight (M8) engine, introduced in 2016, is a prime example.

The Milwaukee-Eight was a significant milestone for Harley-Davidson, marking the first major redesign of its V-twin engine since the Twin Cam 88 in 1999. The M8 was designed to deliver more power, better efficiency, and improved reliability. However, the early iterations of this engine, particularly those built between 2017 and 2019, were plagued by a series of oil-related issues that have left many riders wary of purchasing used models equipped with this engine.

The Milwaukee-Eight’s Oil-Related Problems

The issues with the early M8 engines were not related to leaks or poor build quality but rather to how oil moved through the engine under certain conditions. One of the most common problems reported by riders was oil sumping. This occurs when oil fails to return efficiently to the oil tank and instead accumulates in the crankcase. When this happens, excess oil can increase crankcase pressure, leading to a cascade of issues that can severely impact engine performance.

Symptoms of oil sumping include raised engine temperatures, rough idling, increased engine braking, power loss, and oil aeration as the flywheels rotate in the excess oil. These problems were most commonly reported on Touring models and Softails, particularly those that were ridden hard or used for longer journeys. Without proper intervention, oil sumping can cause significant engine damage, making it a serious concern for owners and potential buyers alike.

Another oil-related issue affecting the 2017-2019 M8 engines was transmission oil migration. In some cases, transmission oil would migrate into the primary housing, resulting in low transmission oil levels and higher primary oil levels. This problem further complicated the engine’s performance and reliability, adding to the growing list of concerns for early M8 owners.

Harley-Davidson’s Response

Recognizing the severity of these issues, Harley-Davidson took steps to address the problems. The company introduced a series of hardware revisions, including an updated oil pump and improved venting systems, aimed at enhancing oil flow and efficiency. These changes were implemented gradually, with the most significant improvements seen in the 2020-2021 model years. By this time, reports of oil sumping and other oil-related issues had dropped off significantly, indicating that the revisions had largely resolved the problems.

What This Means for Used Harley-Davidson Buyers

For those considering purchasing a used Harley-Davidson with an early M8 engine, caution is advised. While not every engine was affected by these issues, the problems were significant enough to warrant attention. Buyers should be particularly wary of models from the 2017-2019 model years, as these are the most likely to have experienced oil-related issues.

When inspecting a used Harley-Davidson with an M8 engine, it’s essential to look for signs of oil sumping or other related problems. These may include unusual engine noises, fluctuating oil levels, or visible oil leaks. Additionally, buyers should inquire about any service bulletins or repairs that may have been performed to address these issues. A well-maintained bike with documented repairs may still be a good investment, but it’s crucial to do thorough due diligence before making a purchase.

The Legacy of the Milwaukee-Eight

Despite the initial challenges, the Milwaukee-Eight engine has proven to be a robust and capable powerplant. The issues with the early models were significant but not insurmountable, and Harley-Davidson’s commitment to addressing them has helped restore confidence in the engine. For riders who prioritize performance, reliability, and the unmistakable Harley-Davidson experience, the M8 remains a compelling choice.

As with any used motorcycle purchase, knowledge is power. Understanding the potential pitfalls of the early M8 engines can help buyers make informed decisions and avoid costly surprises down the road. Whether you’re a seasoned Harley enthusiast or a newcomer to the brand, taking the time to research and inspect a used bike thoroughly can ensure that you ride away with a machine that delivers the performance and reliability you expect.

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