From Past to Present – A History and Roadmap of Harley-Davidson Engines

The world of Harley-Davidson motorcycles is adorned with iconic names like Panhead, Shovelhead, Knucklehead, Evo, and a series of numerical designations such as 103, 107, and 114. To the unacquainted, these may seem like a jumble of words and numbers, but to those familiar with the terminology, they represent significant milestones in the evolution of Harley-Davidson motors. These engines have shaped the course of the company’s history and propelled them to the forefront of V-twin engine development. In this article, we will delve into the captivating journey of Harley-Davidson’s engine development, spanning over nine distinct eras since the early 1900s when the legendary 45-degree V-twin engine, also known as the “F-Head,” was first introduced.

Over the years, Harley-Davidson has traversed a winding road of innovation and refinement, culminating in the present-day utilization of powerful engines such as the 107, 114, 117, and Evolution motors. Each generation of engines has played a crucial role in driving future advancements and enhancing technological prowess. Through continuous improvements, Harley-Davidson remains at the cutting edge of V-twin engine development.

In the following sections, we will take an in-depth look at the captivating history of Harley-Davidson’s engine development, segmented by era. Additionally, we will provide valuable insights to help decipher the various sizes and specifications of HD motors. Join us on this fascinating journey through time and discover the remarkable evolution of Harley-Davidson’s iconic engines.

The Journey of the Big Twin: A Timeline of Harley-Davidson Engines, by Generation


Let’s travel back in time to when it all began more than 100 years ago to have a better understanding of how Harley-Davidson came to the motors it utilises in the motorbike portfolio it offers today. That’s true, the initial F-Head engine was one of the first 45-degree V-twin engines utilised, debuting with the 1911 model year of bikes and continuing until 1929 in manufacturing. The F-head engines were 1000cc or 1210cc intake over exhaust (IOE) motors that were available in 61 or 74 cubic inch configurations. The F-Head engine would eventually be replaced by the Flathead engine starting in 1929, just months before the Great Depression began, and Harley-Davidson would continue to use the 45-degree V-twin chassis for subsequent engines for the following several decades and beyond.


The 74 cubic inch V variant of the Flathead, which debuted in 1930 and was designed to compete with the 74 cubic inch Indian Chief, was introduced initially as a 45 cubic inch motor. Both 737cc and 1212cc versions of the Flathead engines were offered, with the newer U series motors beginning to replace the older V models in 1937 and the UH series offering an 80 cubic inch motor from 1937 to 1941. Up until the 1970s, the Flathead was still manufactured; at that time, it was most notably used as the engine for three-wheeled Servi-Car delivery vans.


The first Harley-Davidson engine to use overhead valves and a more modern oil lubrication system was the Knucklehead engine, which was introduced in 1936 and is known for its distinctive rocker boxes. The Knucklehead had a 983–1212cc range and was offered in 61 and 74 cubic inch models. Production continued until 1947, after which a Panhead engine of a comparable capacity took its place in 1948. The Panhead engines were the first Harley-Davidson motors with hydraulic valve lifters and aluminium heads, and they were a favourite among Harley-Davidson aficionados.



The Shovelhead replaced the Panhead in 1966 and had bigger 74 and 82 cubic inch versions with iterations ranging from 1212 to 1343cc. The heavier bikes of this era led to the development of bigger engines, which delivered more power to the wheels than earlier engines in order to offset the increased weight. AMF took over the manufacturing of Harley-Davidson motorcycles during the Shovelhead era in 1969; while this ownership kept the business financially afloat during the boom in Japanese motorcycle sales that occurred in the 1960s and 1970s, it also signalled an era of decreased manufacturing quality and diminished owner pride. When Harley-Davidson was able to repurchase control from AMF in 1981, the AMF era came to an end.


The Shovelhead continued to be produced through the purchase and selling of Harley-Davidson from AMF up to 1984, when it was replaced by the aptly titled 80ci Evolution engine. From 1984 to 1999, the Evolution motor was in use. It debuted at the same time as the business underwent a rebranding rebirth to separate itself from the AMF period and reignite the sense of ownership and community it had lost in the years before. Although the 1343cc Evolution (or “Evo”) motor was more technologically sophisticated than preceding engines and operated smoother and cooler than those engines, it had a noteworthy problem with oil circulation.


The 88ci engine that launched the Twin Cam era in 1999 was followed by versions with 93, 103, and 110 cubic inches as well as the 88B motor, which was only found in Softail models. The Twin Cam offered the choice of either a carbureted or fuel-injected motor, a dual-coil ignition system, and an upgraded internal oil pump to address the oil problems with the Evo motors. The 1442 to 1687cc Twin Cam motors were more potent than the Evo motors, with higher horsepower and torque ratings than their Evo forerunners.


With the introduction of the Revolution motors in 2001, a new form of V-twin appeared. These engines were 60-degree V-twins, a change from the several generations of 45-degree V-twins that came before them, and they were the stock option for V-Rods starting in 2001. The water-cooled Revolution engines initially had a 69ci displacement before being increased to a 76ci displacement beginning in 2008. In order to build a counterbalanced engine that would help Harley-Davidson compete with the rising sales of Japanese sportbikes and metric cruiser motorcycles, Porsche and Harley-Davidson formed a commercial relationship.


The “Big Twin” Milwaukee-Eight Wafflehead engine used in modern Harley-Davidson bikes gets its moniker from the way its valve covers strikingly resemble waffle irons. 2017 saw the release of the 107ci and 114ci variants of the Wafflehead, while 2018 saw the introduction of the 117ci edition in CVO models. The 107ci and 114ci variants of these engines, with displacements ranging from 1746cc to 1923cc, were offered as both air-cooled (107ci exclusively for the 2017 model year, and Softail models starting in 2018) and water-cooled (for both 107ci and 114ci versions). The Wafflehead motor, as opposed to the Revolution motor, reverted to the 45-degree V-twin configuration and was counterbalanced to enhance the riding experience and lessen vibration.



How to Interpret Engine Sizes

Understanding the various engine types and sizes found in Harley-Davidson motorcycles can be overwhelming. To make sense of it all, let’s delve into the history and categorization of these engines.

In the earlier days, Harley-Davidson engines were commonly known by their nicknames, like Knucklehead or Shovelhead, rather than their actual sizes. From 1936 to 1965, Harley-Davidson bikes featured 61 and 74 cubic inch (ci) engines, ranging from 1000 to 1212 cc. The 74 ci engine continued into the Shovelhead era, while the 80 ci motor was introduced and persisted throughout the Evolution era. The Twin Cam 88 debuted in 1999 with its 88 ci engine, followed by the Twin Cam 95 the next year, marking the era of numeric engine designations for non-vintage motorcycles.

For modern motorcycles, determining the engine size is relatively straightforward: it is often indicated by the cubic inch measurement. Engines measuring 96, 103, 110, 114, or 117 cubic inches are commonly referred to by their numerical sizes, such as “103” or “114.” The air intake badges on these motorcycles usually match the cubic inch size of the engine. As a general rule, the engine size follows a chronological sequence from smallest to largest, with the 96 ci motor being older and the 117 ci motor being newer. (Note: The current generation of engines is technically known as the Wafflehead, but they are colloquially referred to as “107” or “114,” not by the Wafflehead name.)

However, when it comes to current generation Sportsters, the engine size is typically accompanied by the Sportster identifier. These bikes offer two engine options: 883 cc and 1202 cc. Therefore, they are commonly referred to as “Sportster 883” or “Sportster 1200.”

Additionally, there are some important details to consider regarding the larger, non-Sportster engines. The CVO (Custom Vehicle Operations) motors initially featured 1800 cc Twin Cam 110 engines, which later transitioned to 114 ci motors for 2017 models. Since 2018, CVO motorcycles have been equipped with 117 ci motors.

To simplify this wealth of information and minor intricacies, refer to the following chart for a clear overview of Harley-Davidson motorcycle engine sizes:

With this guide at your disposal, you can now navigate the complexities of Harley-Davidson motorcycle engine sizes with ease. Whether you’re a vintage enthusiast or a rider of modern machines, understanding these distinctions will enhance your knowledge of these iconic motorcycles.


Harley-Davidson Engine Size Chart


In The Future…

The future holds exciting prospects for Harley-Davidson as they venture into engine modifications and embrace new technological breakthroughs. While the introduction of the LiveWire electric motor and the revolutionary Revolution Max 60-degree V-twin in the Pan America have showcased their commitment to diversification, the timeless 45-degree V-twin engine remains an iconic trademark of the company. As enthusiasts eagerly await forthcoming engine updates, it is anticipated that these changes will not only uphold the brand’s heritage but also enhance its legacy. Only time will reveal the extent of Harley-Davidson’s innovative strides in engine design and the remarkable advancements that will accompany them.

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