Time Traveler: 1939 BMW R51

Originally delivered to the German SS, this R51 somehow found its way to California.

| March/April 2018

1939 BMW R51
Engine: 494cc air-cooled OHV opposed-twin, 68mm x 68mm bore and stroke, 6.7:1 compression ratio, 24hp @ 5,500rpm
Carburetion: Two 22mm Amal
Transmission: 4-speed, shaft final drive
Electrics: 6v, magneto w/coil and breaker points ignition
Frame/wheelbase: Dual downtube steel cradle frame/55in (1,397mm)
Suspension: Telescopic forks front, plunger coil springs rear
Brakes: 7.9in (200mm) SLS drum front and rear
Tires: 3.5 x 19in front and rear
Weight (dry): 401lb (182kg)
Fuel capacity: 3.7gal (14ltr)
Price then/now: $620 (1,550 marks)/$15,000-$30,000

Imagine if you will that it's April 12, 1939. You're in Berlin, Germany, standing outside a building known as the SS Hauptamt, the headquarters of the Third Reich's Schutzstaffel, an organization more familiarly known as the treacherous SS.

Nearby, a delivery truck rolls to a stop in front of the building. Strapped to the truck's flatbed is the very 1939 BMW R51 featured here. Officially, the bike bears frame number 509728 and engine number 504413, signifying that it was manufactured only a few weeks before, on March 24, 1939, to be exact. As the sleek bike is ceremoniously rolled off the truck and onto the cold, hard pavement, an SS officer signs a document confirming the bike's delivery. The BMW is now part of the Schutzstaffel's motor pool, and will eventually have a role of sorts, perhaps transporting SS couriers or even ranking SS officers from one station to the next as the Third Reich's vast military juggernaut begins its deadly sweep across Europe.

R51 roots

We don't know who within the SS rode this particular BMW, but one thing we know for sure about the R51 model is that it was based on the highly touted R5 (Motorcycle Classics, July/August 2016) designed by Leonard Ischinger and first offered in 1936. BMW aficionados call the R5 Germany's first superbike, and author Ian Falloon, in The Complete Book of BMW Motorcycles, spells out just how important the new model was: "The R5 was arguably the most advanced motorcycle available at that time, not only looking much more modern than the R17 with its pressed-steel frame, but it was significantly lighter and cost only 1,550 marks. Overnight, BMW had made its R17 sporting flagship obsolete."

The R5's engine, a design that carried over to the R51 platform, was BMW's first opposed-twin that didn't use split engine cases; the R254-model 494cc overhead-valve engine utilized a single-piece tunnel-type case, with the crankshaft installed and removed from the front. Timing chains drove the two camshafts positioned slightly above and to each side of the crank, allowing the valve gear in each cylinder head to use shorter tappets and pushrods than previous BMW opposed twins. The valve gear was actuated by rockers moving on needle roller bearings and tensioned with hairpin springs.

Mounted on top of the unit engine case sat the Bosch generator; the distributor and coil were tucked with Teutonic efficiency neatly under the front engine cover. The R5's 22mm Amal carburetors were positioned on either side of the engine, each feeding its own cylinder head. The 4-speed transmission had its foot-shift linkage on the left side; on the right was a hand-lever used primarily for quickly shifting the transmission into neutral for stops. The positive-stop foot gearshift design was based on a system developed by Englishman Harold Willis in 1928 for Velocette. This basic engine and transmission package remained a part of the R51 design that bowed in 1938.

3/29/2018 11:16:55 AM

I joined the US Army upon graduating high school. Stationed in France where I bought an R-25 which I rode winters and summers. It started first easy kick, no matter the circumstances. One night bar hopping with my buds, I carried four of them as passengers a few blocks.

3/29/2018 8:39:57 AM

1958 I was stationed in Germany in the Air Force. I'd bought a 1949 R24 , my first motorcycle. A Major had his R51-2 for sale . I drove it around but wasn't impressed. I was amazed as I could not see my feet under the carbs and besides, why would I need all that power ? Still wish I had..

3/19/2018 11:29:58 AM

I’m surprised at the use of British Amal carbs. I also find it interesting that in the 1930s during the global Great Depression and German hyper-inflation BMW sales increased.

Ride 'Em, Don't Hide 'Em Getaway

Classic Motorcycle Touring and Events.

The latest classic motorcycle events and tours.