It features five SpinScrub brushes for a deep, fresh clean and a wash tool for cleaning upholstery, stairs and carpets. The first and most important step is to keep your chimney clean. Step 5: Open the shutoff valve. The official name for the overhead-valve V-twin was the “61 OHV,” but riders soon dubbed it the “Knucklehead” due to its valve covers, which looked like fists with two knuckles sticking out. A rather odd 35.6-cubic-inch fore-and-aft flat twin was introduced in mid-1919 but would last only until 1923. Meanwhile, the V-twin, which had grown from 50 cubic inches to 61 for 1912, was joined by a 74-cubic-inch version in 1921 — the first of the famed “Seventy-fours.” Improvements were made to the V-twin’s original IOE design over the years, but by the late 1920s they still had exposed valve trains that were messy to run, difficult to maintain, and highly susceptible to wear. This is surprising not only because so little time had elapsed since the flathead’s debut (the previous IOE design was on the market for over 20 years), but also because the initial decision and engineering work took place during the darkest days of the depression.

During the depths of the Great Depression that followed, Harley’s sales fell to less than a fifth of what they’d been before the crash. Among them was the Indian Motorcycle Company, founded in 1901, which would later become Harley’s biggest competitor. Factory horsepower charts showed that Harley’s flatheads slightly out-produced its similar-sized F-heads, most of the advantage coming (surprisingly) at high rpms. Despite the flathead’s virtues, Harley-Davidson felt a more advanced motor would be needed to keep the company competitive in the coming years. Keep reading to learn about the next chapter in Harley-Davidson history. Keep reading to learn about Harley-Davidson’s early years.S. Continue reading for more Harley-Davidson history. Three motorcycles were built that year, and the Harley-Davidson Motor Company was in business. That first Harley-Davidson differed little from other motorcycles of the time, essentially being a bicycle powered by a simple single-cylinder motor that drove the rear wheel through a leather belt. Introduced at a motorcycle show late in 1907, the first production model was released in 1909 with vacuum-operated intake valves and belt drive-both normal Harley-Davidson practice at the time. Though flatheads (also known as side-valves) were theoretically less efficient than overhead-valve or even F-head (intake over exhaust) configurations, flatheads were far easier to service and had evolved to the point where power output was competitive-both of which had been proven and capitalized upon by Indian.

Few could argue that Harley-Davidson is a name recognized — and revered — the world over. Harley-Davidson introduced one of the industry’s first clutches in 1912, and chain drive became available in 1913. A two-speed rear hub debuted for 1914, followed by a proper three-speed transmission for 1915. Singles were sold alongside V-twins during this period, but they would come and go in future years. Aside from the OHV motor, the E-Series introduced two more innovations: a four-speed transmission and the now-famous tank-mounted instrument panel. In 1941, a larger 74-cubic-inch version of the OHV appeared under the F-Series designation. World War II prompted both a military version of the Forty-five and a special horizontally opposed flathead twin with shaft drive that was designed for desert use. As it turns out, the revered Knucklehead lasted only a dozen years on the market (and World War II took a chunk out of that), but its influence was far greater than the figure would imply.

This article traces the development of the machines themselves, but also the legacy contributing to that indefinable element known as the “Harley mystique.” While the reasoning behind this phenomenon might be hard to pin down, the response is not: Harley enthusiasts are among the most devoted followers in the world. But the company managed to keep its head above water while many others were going under, and as the economy began to recover in the mid-1930s, Harley found itself with fewer competitors and an eager clientele. Technology then began advancing at a rapid rate. Work began on a new overhead-valve V-twin in 1931, and though it would take five years to come to fruition, the resulting “Knucklehead” would prove a historic advancement. Even after the Knucklehead was introduced in mid-1936, both the 74- and 80-cubic-inch Big Twins remained in the line, as did the 45. Though the 80 would be dropped after 1942 with the 74 following suit after ’48, Harley-Davidson continued to offer a smaller-displacement flathead V-twin until the mid-1950s. With the quest for more speed came the need for more power, and Harley-Davidson answered with its now-famous V-twin motor. But along with the new motor’s overhead valves came a recirculating oiling system, and that was new to Harley-Davidson.