The BMW R 75/6 holds a unique place in motorcycling history as the first ‘750’ boxer to standardise the Hella switchgear and the transition to a five-speed transmission, solving the ‘gappy’ ratios found in the previous /5 series. It was also the model that introduced the ATE swinging-caliper front disc brake to the mainstream BMW lineup, a significant leap in stopping power for the mid-70s touring market.
| Parameter | Specification |
|---|---|
| Production Years | 1973-1976 |
| Engine Type | Air-cooled, four-stroke opposed twin (Boxer) |
| Oil Type | SAE 20W-50 API SF/SG |
| Oil Capacity | 2.25 L |
| Front Tire | 3.25 S 19 |
| Rear Tire | 4.00 S 18 |
| Front Tire Pressure | 1.9 bar (27.5 psi) |
| Rear Tire Pressure | 2.1 bar (30.5 psi) |
| Battery Type | 52515 (12V 25Ah) |
| Spark Plugs | Bosch W7DC / NGK BP6ES |
Engineering Overview
The R 75/6 is powered by a 745cc air-cooled boxer engine. Unlike the high-revving Japanese multi-cylinder bikes of the era, the R 75/6 focused on torque delivery and long-distance reliability. The inclusion of Bing 32mm constant velocity (CV) carburetors provided smooth throttle response across the altitude changes common in European touring. The chassis utilized a double-loop cradle frame with a bolt-on rear subframe, providing the rigidity necessary for sidecar use, a hallmark of BMW’s modular design philosophy.
Maintenance & Lubrication Guide
For the R 75/6, maintaining the correct oil chemistry is critical. We recommend a high-quality mineral SAE 20W-50 with API SF or SG ratings. Modern oils (SN/SP) often lack the ZDDP (Zinc) levels required to protect the flat-tappet camshafts and lifters found in this vintage boxer. The oil capacity is 2.25 liters; always check the level with the dipstick resting on the threads, not screwed in.
Ignition and Electrical
The electrical system is supported by a 52515-type 25Ah battery. Given the age of these machines, ensuring clean ground contacts is essential for the Bosch starter motor to function effectively. Spark plugs should be gapped according to factory specs using Bosch W7DC or NGK BP6ES equivalents to ensure complete combustion of the air-fuel mixture provided by the Bing carburetors.
Tires and Handling
The R 75/6 uses a 19-inch front and 18-inch rear wheel setup. For solo riding, tire pressures should be maintained at 1.9 bar (front) and 2.1 bar (rear). If riding with a passenger or heavy luggage, the rear pressure should be increased to 2.3 bar to prevent sidewall overheating and maintain tracking stability.
Editorial Verdict
At MotoSpecsLab, we consider the R 75/6 the ‘sweet spot’ of the /6 series. It offers a more refined power delivery than the R 60/6 and lacks the vibration-heavy characteristics sometimes found in the larger-bore R 90/6. It remains one of the most usable and collectible vintage motorcycles for the modern enthusiast who values engineering longevity over outright speed.