| MODEL | BMW R 45 1980 - 1981 |
| Year | 1980 - 1981 |
| Engine Type | Four stroke, two cylinder horizontally opposed boxer, pushrod operated OHV, 2 valves per cylinder |
| Displacement / Capacity | 473 cc / 28.9 cu in |
| Bore X Stroke | 70 x 61.5 mm |
| Compression Ratio | 9.2:1 (35 hp) / 8.2:1 (27 hp) |
| Cooling System | Air cooled |
| Max Power | 26 kW / 35 hp @ 7250 rpm; 20 kW / 27 hp @ 6500 rpm |
| Max Torque | 37.5 Nm / 27.7 lb-ft @ 5500 rpm (35 hp); 31.3 Nm / 23.1 lb-ft @ 5000 rpm (27 hp) |
| Ignition | Battery coil ignition; Bosch contactless electronic ignition from 1981 |
| Induction | 2 x Bing constant-depression carburettors |
| Start System | Electric & kick |
| TRANSMISSION SPECS | |
| Lubrication | Wet sump |
| Gear Box | 5 Speed |
| Clutch | Single plate, dry, diaphragm spring |
| Final Drive | Shaft |
| CHASSIS SPECS | |
| Frame | Double loop frame of oval steel tubes with bolt-on rear section |
| Front Suspension | Telescopic hydraulic fork, 175 mm / 6.9 in travel |
| Rear Suspension | Long swing arm with adjustable struts, 110 mm / 4.3 in travel |
| Front Brakes | Single 260 mm disc, 2 piston caliper |
| Rear Brakes | 200 mm drum |
| DIMENSION SPECS | |
| Overall Length | 2110 mm / 83.1 in |
| Overall Width | 688 mm / 27.1 in |
| Overall Height | 1080 mm / 42.5 in |
| Seat Height | 750 mm / 29.5 in |
| Wheelbase | 1400 mm / 55.1 in |
| Ground Clearance | — |
| Dry Weight | 185 kg / 408 lbs |
| Wet Weight | 205 kg / 452 lbs |
| WHEEL SPECS | |
| Front Tyre | 3.25 - 18 |
| Rear Tyre | 4.00 - 18 |
| FUEL SYSTEM | |
| Fuel Capacity | 22 Litres / 5.8 US gal |
| Fuel Consumption | 4.5 L/100 km / 52 mpg US |
| Top Speed | 160 km/h / 99 mph (35 hp); 145 km/h / 89 mph (27 hp) |
By 1980 the R 45 was in its third season as BMW's entry-level boxer, still offered in a low-insurance 27 hp tune for Germany and a 35 hp version elsewhere. The mechanics stayed essentially as launched, while the 1981 model year brought contactless electronic ignition and a stronger 300 W alternator. It remained a frugal, smooth shaft-drive commuter and tourer rather than a fast bike.
