While often overshadowed by its larger sibling, the R 1100 GS, the BMW R 850 GS (R259) is regarded by engineering purists as the most balanced boxer of its era. A unique historical highlight of this model is its short-stroke engine configuration; by utilizing a smaller 87.8mm bore compared to the 1100’s 99mm while retaining the same stroke, BMW created an engine with significantly lower secondary vibrations and a much smoother power delivery, making it a cult favorite for long-distance touring.
| Component | Specification |
|---|---|
| Production Years | 1998 – 2001 |
| Engine Type | Air/Oil-cooled, 4-stroke Flat Twin (Boxer) |
| Engine Oil | SAE 20W-50 (API SF/SG/SH) – 3.75 Liters |
| Spark Plug | Bosch FR6DDC |
| Front Tire | 110/80 R 19 59H |
| Rear Tire | 150/70 R 17 69H |
| Battery | 51913 (YT19BL-BS) |
Engineering Overview: The R259 Platform
The R 850 GS utilizes the sophisticated R259 chassis, characterized by its lack of a traditional frame. The engine acts as a load-bearing element, connecting the Telelever front suspension to the Paralever rear swingarm. This setup virtually eliminates brake dive, a critical advantage for an adventure-touring motorcycle weighing approximately 243kg wet.
Maintenance Guide & Technical Essentials
1. Lubrication System
The R 850 GS is highly sensitive to oil quality. We recommend a high-zinc SAE 20W-50 mineral or semi-synthetic oil to protect the flat-tappet cam followers. The total capacity is 3.75 liters when replacing the filter. Always check the oil level via the sight glass only after the engine is at full operating temperature and has sat on the center stand for 10 minutes.
2. Ignition & Electrical
To maintain the smooth idle the 850 is known for, the dual-electrode Bosch FR6DDC spark plugs must be gapped correctly and replaced every 20,000 km. The electrical system relies on a high-capacity 51913 (YT19BL-BS) battery; given the ABS system’s sensitivity to voltage drops during startup, maintaining a healthy charge is paramount to avoid ‘ABS fault’ lights.
3. Chassis & Tires
Proper inflation is critical for the R 259’s neutral handling characteristics. For solo riding, maintain 2.2 bar (32 psi) Front and 2.5 bar (36 psi) Rear. When fully loaded with panniers and a passenger, increase pressures to 2.5 bar (36 psi) and 2.9 bar (42 psi) respectively to prevent carcass deformation and overheating.
MotoSpecsLab Verdict
The BMW R 850 GS represents a ‘sweet spot’ in BMW’s Motorrad history. It offers the ruggedness of the GS line with a level of mechanical refinement the larger displacement models of the time couldn’t match. For the modern owner, following these technical specifications ensures this over-engineered boxer will easily surpass the 200,000 km mark.