Harley-Davidson soon realized that the easiest way to significantly increase engine size was to add an extra cylinder. The company built a prototype V-twin in 1907 and four years later the first production V-twins rolled out of the factory. The engine effectively joined two singles on a common crankshaft and cases. If the angle of the "V" was narrow, the new engine could be used in the same frame as a single. Harley chose a 45° "V," and a motorcycling classic was born. The arrival of the mechanical exhaust valve on the V-twin was also important, allowing engine revs to be increased and thus release more power. Harley's trademark is born The appearance of the 45° V-twin effectively provided the blueprint for the Harley twin of today. From 1915 it was refined and improved rather than radically altered. F-Head set-up These early V-twins were known as F-heads because the inlet valve was positioned in the cylinder head and the exhaust valve was on the side of the cylinder, creating an "F" formation. This incomplete engine is believed to be from a factory race bike. V-twin operation To make a V-twin, the two rods connecting the crankshaft to the pistons have to sit on the same shaft. Harley used "male and female" rods to solve the problem. "The V-twin opened up America for ordinary riders. It was a giant step forward for the Harley rider." Bruce Lindsay (Motorcycle Restorer) The Competition. 1914 YALE V-TWIN Harley wasn't the only manufacturer to choose the 45° engine layout for its bikes. The Consolidated Manufacturing Company of Toledo, Ohio, built Yales from 1903-15 and this 61cu. in. model had a 45° V-twin engine and mechanically operated inlet valves.
SPECIFICATIONS. 1915 KR Fast Roadster Engine: Inlet-over-exhaust, V-twin Capacity: 6l cu.in. (1000 cc) Power output: 15 bhp Transmission: Single-speed competition gearbox, chain drive Frame: Tubular loop Suspension: Leading-link front forks, rigid rear. Weight: 325 lb (147kg) Top speed: 80 mph (130km/h) THE IDEA OF A RACE BIKE on the road has always been attractive to motorcyclists. Modern bikers relish the power, handling, and brakes of competition-developed machinery and pioneer motorcyclists were no different. Harley's Fast Roadster was based on the board-track racer but fitted with mudguards, a chainguard, and conventional handlebars. Who needed a gearbox or lights? It was built for amateur racers at a time when Harley-Davidson's factory race team was starting to taste success; the K-series won a number of 100- and 300-mile (161- and 483-km) races for Harley in 1915. With just over 100 built, this model is now very rare. 1915 KR Fast Roadster The "close coupled" frame on the KR was shorter than that fitted to other models such as the F because no gearbox was fitted. A short wheelbase traditionally offers better handling at the expense of comfort and stability. Wide handlebars One of the civilizing features which the Fast Roadster acquired from its conventional road-gomg stablemates was a set of pulled-back handlebars. These offered a combination of comfort and control on the road. Racing handlebars would haw been suitable only for short trips to the osteopath.
SPECIFICATIONS. 1915 KT Board Racer Engine: Inlet-over-exhaust, V-twin Capacity: 61 cu.in. (l000cc) Power output: 15 bhp Transmission: Three-speed, chain drive Frame: Tubular loop Suspension: Leading-link front forks, rigid rear Weight: 325 lb (147kg) Top speed: 80 mph (130km/h) Harley-Davidson did not participate in team racing until 1914, when it decided to exploit the potential benefits of publicity and development that could be derived from racing success. Board-track racing was reaching new levels of popularity, with promotors able to attract huge paying crowds to the meetings, so Harley's decision to enter into competition made a lot of sense. And the move paid off almost immediately, as the Harley race team began to achieve significant results in 1915 on bikes such as this KT. In September 1915, an F-head Harley set a 100-mile (161-km) record of 89.11 mph (143.46 km/h) on a board track in Chicago. It all augured well for the launch of the famous eight-valve racer a year later. 1915 KT Board Racer Board racers were spindly, frail-looking machines that were stripped of surplus equipment. There was no gearbox and usually no brakes, though this bike is fitted with a rear drum. Their appearance belied their astonishing strength and performance — these bikes could be run flat-out for considerable distances, with 100-mile (161-km) races not uncommon on the banked wooden tracks. Maywood Speedway Park, 1915 Mawood Park was a typical board-track venue. Tracks were constructed by placing thin planks on a wooden frame. With use, the boards became covered in oil arid rubber, gradually making them more slippery and dangerous. Despite the initial success of this form of racing, injury and death were not uncommon arid the deaths of spectators m the early 1920s saw the sport go into terminal decline.
The Early Single-Cylinder gasoline engine was underpowered and inefficient, though Harley's singles were among the best available. The "atmospheric" inlet valve relied on a light spring to keep it closed and was forced open by the pressure created from the falling piston. The system was simple, but it couldn't work properly at anything other than slow engine speeds. Increasing capacity boosted the power output, but it was no substitute for improved efficiency. The Наrley single was just a good solid dependable motorcycle at a time when most of them were not. Richard Rosenthal (Motorcycle Historian) Rugged and dependable In an era of unreliable and uncomfortable motorcycles, the Harley single stood out as a solid workhorse capable of covering long distances. The well-made engine got some of the credit, but Harley's sprung seat-post was a welcome feature for the often appalling road conditions. The Competition. 1911 EXCELSIOR MODEL K The Chicago Excelsior company was the third-biggest motorcycle manufacturer in the US until its closure in 1931. Like the Harley, this machine had belt-drive, but used the engine cases as part of the frame, as opposed to Harley s loop-frame system. Single with Bosch magneto A magneto was introduced as an option in 1909. This simple electric generator provided a spark for the ignition system and made the early Harley a more useable machine. No female frills Some European manufacturers offered "ladies' models" with special frames and skirt-guards. Harley women didn't need these luxuries. Inlet-over-exhaust The inlet valve was kept closed with the exposed spring on the top of the cylinder. As the piston fell, it created a vacuum in the cylinder, resulting in the valve being forced open by atmospheric pressure. A charge of fuel and air mix was then sucked in through the carburetor.
SPECIFICATIONS 1912 Silent Gray Fellow Engine: Inlet-over-exhaust, single-cylinder Capacity: 30cu. in. (494cc) Power output: 6.5bhp @ 2,700rpm Transmission: Single-speed, belt drive Frame: Tubular loop Suspension: Leading-link forks, rigid rear Weight: 195 lb (89kg) Top speed: 45mph (72km/h) By hie time Harley-Davidson built this X-8 single in 1912, the company was well on the way to establishing itself as a major motorcycle manufacturer, and the motorcycle was a more refined mode of transportation. The rugged engineering and rigorous development championed by Harley from day one had borne fruit in the form of sprung forks and magneto ignition, and the company wasted no time emphasizing that cubic inches were the key to increased power. The original 1903 Harley had a 24.74cu. in. (405cc) engine, rising to 26.8cu. in. (440cc) in 1906, and 30cu. in. (494cc) in 1909. In 1913 it gained a further 5cu. in. (82cc). The Harley single became a valued and dependable machine which earned it the nickname "Silent Gray Fellow." 1912 Silent Gray Fellow This bike was a direct development of the original 1903 model and continued in production until 1918. Though it still had belt final-drive, an atmospheric inlet valve, and no gearbox, these developments were just around the corner. Technical advances The optional rear hub clutch on this model meant that the bike could be stopped without stalling the engine, and the optional Schebler carburetor hugely improved reliability over early models.
SPECIFICATIONS 1905 Model No.1 Engine: Inlet-over-exhaust single Capacity: 24.74cu. in. (405.41cc) Рower output: Unknown Transmission: Single-speed, belt drive Frame: Tubular loop Suspension: None Weight: 185 lb (84kg) Top speed: 40mph (64km/h) (est.) MOTOR AND CYCLE There wasn't much more to the first Harleys than these two vital ingredients. Though William Harley and the Davidson brothers used a larger engine than most of their contemporary manufacturers, the fact that pedal power was an essential supplement to the internal combustion engine on hills meant that the bicycle layout had to be retained. Harley curved the bottom frame tube under the crankcases to allow the engine to be mounted lower in the frame, resulting in superior handling. The battery ignition system, crude carburetor, belt drive, and other unrefined elements ensured that the early motorcycle wasn't really a viable means of transportation, but at least the Model No.1 was a cut above the average. Hurley's Model No.1 was essentially an engine boiled onto a bicycle frame, with pedal-power still needed when there was a steep hill to be climbed. 1905 Model No.1 The 1905 Model No.1 was almost identical to the bikes built in 1903 and '04, and until 1909 Harley-Davidson produced only one model, which was improved upon each year. The model number represented the year of production minus four.