| Specification | Data |
|---|---|
| Production Years | 1982 – 1990 |
| Engine Oil | SAE 20W-50 API SE/SF/SG (3.5 L) |
| Tires (Front/Rear) | F: 100/90 – 18 56V / R: 130/90 – 17 68V |
| Tire Pressure | F: 2.2 bar (32 psi) / R: 2.5 bar (36 psi) |
| Battery | 52515 (12V 25Ah) |
| Spark Plugs | Bosch X5DC |
Engineering Highlight: The Flying Brick
The BMW K 100, internally designated K589, represents one of the most radical departures in motorcycle engineering history. While BMW was synonymous with the Boxer twin, the K 100 introduced the “Compact Drive System.” The unique engineering highlight of this machine is its longitudinal inline-four engine laid on its side (90 degrees). This configuration, which earned the bike the nickname “The Flying Brick,” allowed for a low center of gravity and direct shaft drive alignment, effectively solving the cooling and packaging issues inherent in traditional across-the-frame fours of the early 1980s.
Technical Review: Performance and Reliability
At MotoSpecsLab, we classify the K 100 as a milestone in high-mileage touring. The 987cc liquid-cooled engine was pioneering for its time, utilizing Bosch LE-Jetronic fuel injection—a technology more common in BMW automobiles than motorcycles of that era. This system provided unparalleled reliability and cold-start performance. The chassis, though heavy by modern standards, offers immense stability at highway speeds, making it a favorite for long-distance enthusiasts and custom builders alike.
Maintenance Guide & Service Intervals
To maintain the structural and mechanical integrity of the K589, adherence to specific fluid and electrical standards is mandatory:
- Lubrication: The engine requires a high-viscosity SAE 20W-50 oil. Given the era of the engine’s design, using an API SE, SF, or SG grade ensures the flat-tappet components receive adequate zinc/phosphorus protection. Capacity is 3.5 liters.
- Ignition: The Bosch X5DC spark plugs are critical for the specific heat range required by the horizontal cylinder head.
- Electrical: A high-capacity 25Ah battery (52515) is necessary to provide the high cranking amps required for the heavy-duty starter motor.
- Tire Care: For optimal handling and to prevent uneven wear on the heavy frame, maintain 2.2 bar (32 psi) in the front 100/90-18 tire and 2.5 bar (36 psi) in the rear 130/90-17 tire.
Frequently Asked Questions (FAQ)
How often should I change the oil?
For the BMW K 100, we recommend changing the 20W-50 oil every 7,500 km (approx. 5,000 miles) or annually, whichever comes first, to prevent sludge buildup in the horizontal oil pan.
Why is the K 100 called the ‘Flying Brick’?
The name refers to the distinctive rectangular shape of the engine block, which lies flat and longitudinal in the frame, resembling a brick flying through the air.
Is the K 100 suitable for modern touring?
Absolutely. Due to its fuel injection and robust shaft drive, many K 100 models easily exceed 200,000 km with regular maintenance of the splines and cooling system.