Harley-Davidson Model W
1921 Harley-Davidson Model W
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| Manufacturer | Harley-Davidson |
|---|---|
| Also called | Sport Twin |
| Production | 1919–1923 |
| Assembly | Milwaukee, WI USA |
| Engine | 35.64 cu in (584.0 cc) side valve flat-twin |
| Bore / stroke | 2.75 in × 3.00 in (69.9 mm × 76.2 mm) |
| Compression ratio | 3.75:1 |
| Power | 6 hp (4.5 kW) |
| Ignition type | magneto (W, WF) battery and coil (WJ) |
| Transmission | 3-speed manual |
| Frame type | tubular steel, single downtube |
| Suspension |
front: trailing link with single coil spring rear: none, rigid |
| Brakes |
front: none rear: contracting band |
| Tires | 26 in × 3 in (660 mm × 76 mm) |
| Wheelbase | 57 in (1,448 mm) |
| Weight | 265 lb (120 kg) (dry) |
| Fuel capacity | 2.75 US gal (10.4 L) |
| Oil capacity | 2 US qt (1.9 L) |
The Harley-Davidson Model W, also known as the Sport Twin, is a motorcycle made by Harley-Davidson from 1919 to 1923. Unusually for a Harley-Davidson motorcycle, the Model W had a flat-twin engine and a trailing link fork. The Model W set speed records on runs from New York City to Chicago and from the Canada–United States border to the Mexico–United States border. Slow home market sales led to the end of production after four years.
Harley-Davidson's intention in introducing a new middleweight model was to increase the size of the motorcycle market by appealing to new riders with an entry-level product. The design imitated the British Douglas motorcycle flat-twin with cylinders in line with the frame, and offered several features that were meant to bring new motorcyclists into the market, including a smoother running engine than a typical Harley-Davidson V-twin, a lower center of gravity for easier handling, and a design that kept the rider and the motorcycle cleaner from oil and the dirt that oil attracted. It was cleaner because there were fewer oil compartments, due to the transmission and clutch being integrated with the engine crankcase, providing fewer ways for the oil to leak. In addition, an optional drive chain enclosure could keep chain lubricant off the motorcycle and the rider's clothing.
The engine components were designed for ease of access and maintenance. The valve guides and valves could be removed without removing the engine from the motorcycle. The cylinder heads were integral with the engine. The intake and exhaust manifolds were cast as one piece such that the exhaust would heat the fuel mixture to improve fuel atomization. The engine had a large external flywheel on the left side similar to that on the horizontal single-cylinder Moto Guzzi.
The Model W engine was Harley-Davidson's first flathead engine, and its transmission was the first in a Harley-Davidson motorcycle to be housed in the engine cases. The transmission included helical gear drive, a wet clutch, and a three-speed gearbox. The engine was a stressed member of the frame.
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