| Component | Specification |
|---|---|
| Engine Oil | SAE 20W-50 API SF/SG/SH (3.75 L) |
| Front Tire | 100/90 V 18 |
| Rear Tire | 130/90 V 17 |
| Tire Pressure (F) | 2.2 bar (32 psi) / 2.5 bar (36 psi) |
| Tire Pressure (R) | 2.5 bar (36 psi) / 2.9 bar (42 psi) |
| Spark Plug | Bosch X5DC |
| Battery Type | DIN 52515 |
Engineering Heritage: The Longitudinal Revolution
The BMW K 100 LT (Luxury Touring) represents a pivotal moment in motorcycle history. While BMW was synonymous with the Boxer engine for decades, the K-series—internally designated K589—introduced the world to the ‘Flying Brick.’ This unique 987cc inline-four engine was mounted longitudinally and laid flat on its side at a 90-degree angle. This radical engineering choice achieved a remarkably low center of gravity while allowing for a direct shaft drive output, a design that remains a masterclass in mechanical efficiency.
Technical Deep Dive: Power and Reliability
Produced between 1986 and 1991, the K 100 LT was the flagship of the range, designed to compete with the heaviest hitters in the touring market. It featured the Bosch LE-Jetronic fuel injection system, which provided smooth power delivery and exceptional cold-start reliability—a rarity for motorcycles of that era. The LT trim specifically added luxury features such as a taller windscreen, integrated luggage, and the sophisticated NIVOMAT self-leveling rear suspension system.
Maintenance Protocol for the K 100 LT
Engine Lubrication
The K 100 LT engine is robust but demands high-quality mineral or semi-synthetic oil. We recommend a SAE 20W-50 viscosity grade meeting API SF, SG, or SH standards. The total capacity is 3.75 liters. Regular oil changes are critical to prevent sludge buildup in the horizontal cylinders.
Ignition System
To maintain the smooth idle and throttle response the Flying Brick is known for, the Bosch X5DC spark plugs must be gapped correctly and inspected every 15,000 km. These plugs are specifically designed to handle the thermal loads of the compact, enclosed engine bay of the LT.
Tires and Safety
Handling on a 250kg+ touring machine is highly sensitive to tire pressure. For the 100/90 V 18 front and 130/90 V 17 rear tires, always adjust for load. Running at 2.5 bar (Front) and 2.9 bar (Rear) when fully loaded with a passenger and luggage is essential to prevent sidewall overheating and ensure stability at highway speeds.
Frequently Asked Questions (FAQ)
Q: Why is it called the ‘Flying Brick’?
A: The nickname refers to the engine’s rectangular, block-like appearance and its orientation, which looks like a brick flying through the air when the fairings are removed.
Q: What is the battery requirement?
A: The K 100 LT uses a DIN 52515 battery. Given the high electrical load of the touring accessories, ensuring a healthy battery is vital for the electronic fuel injection system.
Q: Is the K 100 LT suitable for modern long-distance touring?
A: Absolutely. With its 22-liter fuel tank and ergonomic fairings, it remains one of the most capable vintage tourers available today.