Motorcycle: Singles - Model A & B Single, 1926 -1934
Date: Sunday, October 31 @ 15:57:38 UTC
Topic: Motorcycle, Motorcycles, Motor Cycle
Model A & B Single, 1926 -1934
Although single-cylinder machines were as much a hallmark of Harley-Davidson's formative years as the big V-twins with which they are now associated, Juneau Avenue produced almost no such models from 1919 until 1926. The sole exception was the Model CD, a 37.1 cu in (608cc) machine created by the simple expedient of removing one pot from the 74-inch twin. It was built in very small numbers from 1921 to 1922 and was intended for commercial use only. When singles did reappear, they were considerably smaller than before, displacing just 21.1 cu in (346cc) compared to the earlier 30-inchers.
Somewhat confusingly, the single was known simultaneously as both Model A and Model B. The former denoted a magneto version, the latter that the machine was fitted with a generator and coil ignition. This was further refined into Models AA and BA Sport Solos, where the second letter indicated that the engine had overhead valves. The machine was fitted with a generator and coil ignition. This was further refined into Models AA and BA Sport Solos, where the second letter indicated that the engine had overhead valves. The more basic model, designated by a simple A or B was of straightforward "flathead" design, with valves side-by-side and operated by short push-rods.
The overhead-valve model was an altogether more potent piece of machinery that would achieve considerable competition success as the legendary Peashooter racer. It was inevitably less aggressive in roadster trim, yet still capable of what was then a giddy 4,800rpm and close to 65mph (105kph). Its side-valve sibling, on the other hand, struggled to exceed 50mph (80kph). Despite this marked difference, both engines were rated at 3.31 horsepower. At the time, quoted power figures were not a measure of actual output, merely a function of piston displacement and thus quite meaningless as a reflection of performance. Modern power figures, of course, describe actual output. Strangely, Harley chose to promote the flathead at the expense of the more advanced engine, probably because side-valves would soon comprise the vast bulk of the Milwaukee range.
Mechanically, the engine featured a lightweight aluminium alloy piston (initially iron for the side-valve machines) running in a cast-iron cylinder. Typically for the time, the overhead's valve gear was exposed, although the 21.1 cu in (344cc) single was the first Milwaukee engine lubricated by a proper mechanical pump. Nonetheless, a hand pump was retained for supplementary oiling when the engine was under extreme loads. Transmission was by the now-familiar three-speed sliding gear, driven by a foot-operated single-plate diy clutch.
By the time of the new single's debut in 1926, electrical equipment had leaped forward in specification and dependability. Although full electrical equipment was optional (Models A and AA came as standard with just a magneto to generate sparks), it was also comprehensive. Generator models featured a coil and distributor (to power and time the ignition), battery, horn, two-bulb headlight and tail-light, all controlled from a switch on the steering head — everything you might expect to find on a modern motorcycle, except stop-light and indicators. Less can be said for the cycle parts. True, the single wore the new type of teardrop petrol (gas) tank, which wrapped over the top frame tube rather than hung from it, as before. At the front, Harley's familiar sprung forks gave some comfort and control, but the rear end was rigid and would remain so for more than 20 further years. The rear hub did contain a brake - a 5 3/4 in (146mm) drum — but the front wheel contributed nothing to retardation. It would be another two years before Milwaukee installed their first front brake. During the early 1930s, "21"'s sales were hit, partly by the relative success of the Series C single, but mainly by the Depression. Domestic supplies were halted during 1931 when just three examples were exported. The ohv model never reappeared, although flathead sales rallied slightly before the model was axed at the end of 1934.
Engine: side-valve or overheadt valve single
Capacity: 21.1 cu in (346cc)
Power: 8bhp (side-valve) or 12bhp (ohv)
Wheelbase: 55 in (1,400mm)
Top speed: around 50mph (80kph) (side-valve) or 60mph (96kph) (ohv)
This article comes from Free Vin Check, Get Vehicle History Report, Free Car History, Used Car History, Auto History, Free Vehicle History, VIN Number Check, Car History, Lemon, Check
The URL for this story is: