| Component | Specification |
|---|---|
| Model Years | 1960–1966 |
| Engine Type | 247cc Single-cylinder, 4-stroke |
| Oil Type | SAE 30 (>0°C) / SAE 20 (<0°C) |
| Oil Capacity | 1.1 Liters |
| Tires (F/R) | 3.25 x 18 / 3.25 x 18 |
| Battery | DIN 00811 |
| Spark Plug | Bosch W4AC |
The BMW R 27 holds a unique place in motorcycling history as the final evolution of BMW’s single-cylinder, shaft-driven legacy. While its predecessors were known for their ruggedness, the R 27 introduced a revolutionary engineering advancement: the Schwingmetall rubber engine mounts. This was the first and only BMW single-cylinder model to feature a fully rubber-isolated engine and gearbox, a design choice that significantly mitigated the inherent vibrations of a large single, providing a level of refinement previously unseen in its class.
Technical Engineering & Performance
Produced between 1960 and 1966, the R 27 was powered by a 247cc overhead valve (OHV) engine. It delivered a respectable 18 horsepower at 7,400 rpm, a notable increase over the R 26. This power was transmitted via a four-speed gearbox to the rear wheel through BMW’s signature enclosed drive shaft. The chassis utilized the famous Earles front forks and a rear swingarm, providing exceptional stability and comfort for both solo riders and sidecar enthusiasts.
Maintenance Guide: Keeping the Legend Alive
To maintain the mechanical integrity of the R 27, strict adherence to period-correct fluid specifications is essential. Modern multi-grade oils can sometimes be too detergent-heavy for these vintage seals; hence, MotoSpecsLab recommends high-quality mono-grade oils as originally specified.
Fluid & Lubrication
- Engine Oil: Use 1.1 liters of SAE 30 for standard operation. In colder climates (below freezing), switch to SAE 20.
- Interval: Changes should occur every 2,000 to 3,000 km to ensure the centrifugal oil slinger remains clear of debris.
Tires & Chassis
The R 27 uses identical 3.25 x 18 tires for both the front and rear. Maintaining correct pressures is vital for the longevity of the Earles fork bushings and overall handling stability:
- Front Pressure: 1.5 bar (21.3 psi)
- Rear Pressure: 1.7 bar (24.1 psi)
Electrical System
The electrical system operates on a 6V circuit. The standard battery is a DIN 00811 unit. For ignition, the Bosch W4AC spark plug is the factory-recommended heat range to prevent pre-ignition while ensuring clean combustion across the RPM range.
MotoSpecsLab Editorial Review
The BMW R 27 represents the end of an era. It is a machine of immense character, built with the “no-compromise” quality that defined BMW in the mid-20th century. While it may not match the raw speed of the British singles of the time, its vibration-damped ride and legendary reliability make it one of the most usable vintage motorcycles today. For collectors, the R 27 is not just a motorcycle; it is a masterpiece of mechanical isolation and durability.
Frequently Asked Questions
Q: Why is the rubber mounting so important on the R 27?
A: The rubber mounts decouple the engine from the frame, preventing the high-frequency vibrations of the 247cc single from reaching the rider, which vastly improves long-distance comfort.
Q: Can I use modern 10W-40 oil?
A: While possible, it is not recommended for engines without a modern oil filter. Stick to mono-grade SAE 30 to ensure the oil slinger functions correctly.