From BMW Tech
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After World War II, by Potsdam Agreement of the USSR, USA, and the UK, BMW Aktiengesellschaft was prohibited from building motorcycles . Later, this ban was lifted and in 1948 BMW produced its first postwar motorcycle, the 250 cc R24 (see photo), which was based largely on the prewar R23. It was the only postwar BMW motorcycle produced without a Suspension (motorcycle). BMW introduced the R25 model, with Swingarm, in 1950. The last of the plunger models, the R25/3 (see photo), was introduced in 1953.
In 1956 BMW introduced a completely revamped Four-stroke cycle, the R26 (engine numbers 340 001 – 370 236), with improvements paralleling those introduced at the same time in the boxer twins. The R26 came with an enclosed drive shaft, rear swingarm, and front Earles forks. A new headlight nacelle came with a sliding black plastic over the ignition key, and the “bell-bottom” front fender was dropped along with the mechanics' hand shifter. The engine of the R26 was bolted directly to the frame, and the engine produced 15 hp (11 kW).
Based largely on the R26, in 1960 the R27 added rubber mounts for the engine and boosted power to 18 hp (13 kW).
The R27 was the last shaft drive single-cylinder motorcycle that BMW made. The 247 cc R39 was the first in 1925. The R27's 250 cc Overhead valve vertical single was the only rubber-mounted thumper engine BMW ever produced. The engine pumped out 18 hp (13 kW), the highest ever for a shaft-drive BMW single. BMW manufactured 15,364 R27s (engine numbers 372 001 – 387 566 ) over the production years of 1960 through 1966. Some of the 1966 R27s were sold as 1967 models because dealers in those years often would assign dates to BMW motorcycles when they sold them, and not necessarily when they were manufactured.
The vast majority of R27 motorcycles exported to the United States by BMW were black with white pinstriping. A few, however, were brought in by importer Butler & Smith in a color called Dover white, with black pinstriping. Why "Dover white?" Butler & Smith head honcho, Michael Bondy, had a 1942 Packard automobile in an off-white color called dover white. Bondy sent a sample of this color to BMW AG in Munich and asked that it be duplicated. BMW did copy the color, and Bondy ordered fifty motorcycles in that color. Today, BMW motorcycles in original dover white are a sought-after rarity.
BMW did things differently to other manufacturers. This is evident in the R27. Its enclosed shaft final drive is rare for a single cylinder motorcycle. But it also had a triangulated Motorcycle fork; so the motorcycle had a front swingarm as well as a rear swingarm. When you squeezed the front brake lever hard not only did the front end not dive, it actually rose slightly. Thus, braking was a very steady activity, though the brakes were weak by today's standards. The R27 engine's crankshaft was laid out fore-to-aft, not side- to-side; also a rare feature. This way, the Crankshaft and the final shaft were in line, and drive forces did not have to be run through a set of 90-degree gears. Also, the Kick start swung out sideways instead of parallel to the frame, so kick starting an R27 is a rather easy and danger-free affair.
|Engine Numbers||372 001 – 387 566|
|Design||Single cylinder with driveshaft|
|Engine||Four-stroke cycle, 2 Overhead valve|
|Transmission (mechanics)||Four-speed, left foot|
|Model years||1960 — 1966|
|Power||18 hp (13 kW) @ 7,400 rpm|
|Fuel efficiency||60.3 mpg(US) DIN 70030|
|Maximum speed||81 mph (130 km/h) / with side car 56 mph (90 km/h)|
|Curb weight||357 lb (162 kg.)|
|Gross vehicle weight rating||716 lb / with side car 1,058 lb|
|Tires front & rear||3.25 x 18|
|Battery||6 volts, 9 Ah.|
|Tank capacity||3.96 US gal|
|Engine oil capacity||2.6 US pint|
|Transmission capacity||650 cc|
|Rear drive capacity||125 cc|