Singularly Perfect: 1953 BMW R25/2

“That rekindled my interest in motorcycles,” Tony says, “but, I wasn’t going to be looking for a modern machine.” Indeed, the classic lines of a vintage BMW with its black paint and white, hand-laid pinstripes are what Tony appreciated. “Plus, they seemed pretty elementary in design and I thought they’d be easy to work on,” Tony confides.

The road to the BMW R25/2

His path of BMW discovery started with a friend’s R75/5. “The rudimentary controls and the kickstarter, that all appealed to me,” Tony says. “But the R75/5 is newer and more common. That’s when I discovered its predecessor, the ‘Slash Two’ BMWs.”

In 2007, Tony placed a request on his company’s internal classified ads system, simply stating he was looking to purchase an old BMW. Someone responded, saying there was a BMW languishing in a brother’s garage. Hessner made arrangements and met the son of the elderly owner, who at one time maintained a drinking establishment. Turns out a patron had traded a 1953 BMW R25/2 to settle a debt, but there really wasn’t much other background provided.

With only 11,150 miles on the odometer it was a low-mileage example, but one that had seen better days. It had suffered a piston seizure and was taken off the road in 1974. “It looked like the bike had been laid down on its right-hand side,” Tony says, “and the throttle might have been wide open when the engine seized.” In a box were the cylinder, cylinder head and damaged piston, but other than an errant front mudguard stay the BMW was complete.

Apart from the fact the BMW was a single-cylinder, Tony wasn’t sure what he’d unearthed. Even so, he paid $600 for the bike, loaded it up and took it home. That’s when the research began.

BMW’s single

BMW built its first single-cylinder motorcycle, the R4, in 1932. The R4 had a 398cc overhead valve engine that made 12 horsepower transferred through a 3-speed gearbox, all packaged in a pressed steel duplex frame. A 4-speed transmission was introduced in 1933, and 1934 saw output increased to 14 horsepower.

In 1937 BMW introduced its next generation single, the R20. This machine had a 192cc 4-stroke engine, a 3-speed transmission and shaft final drive, all placed in a bolted-up, double loop steel tube rigid frame with spring-action telescopic front forks. The R20 became the R23 in 1938, and while the chassis and transmission specifications remained the same, engine capacity grew to 247cc. Produced from 1938 to 1940, a little more than 8,000 R23s hit the roads before BMW halted motorcycle production because of World War II.

Postwar, BMW was not immediately allowed to manufacture motorcycles. The situation changed in 1948, when the company was given approval to construct powered single-track vehicles of less than 250cc. According to author L.J.K. Setright in his 1978 book Bahnstormer: The Story of BMW Motorcycles, BMW had been developing a lightweight 2-stroke flat twin of 125cc that never saw production. Instead, because all factory drawings had either been captured or destroyed, BMW essentially reverse-engineered a prewar R23, measuring and replicating many of the prewar components for the newest model, the R24.

Introduced in 1948, the R24 was the first postwar motorcycle from the BMW factory. Again featuring a bolted together steel tube frame with no rear suspension, the single-cylinder engine was similar to that of the R23, with an inline crankshaft supported on ball bearings housed in a single alloy casting that bolted up to the transmission, which now held four gears. Final drive was via shaft. The compression ratio increased slightly, from 6:1 to 6.75:1, and the R24 revved out at 5,600rpm.

According to a 1948 R24 factory brochure, the engine featured “Economy-minded design of combustion chamber due to beautifully shaped, generously dimensioned light-metal cylinder head with large-surface cooling fins and efficient dissipation of heat. Overhead valves arranged Vee-wise in cylinder head; entire valve gear assembly encased for protection from dust and dirt.” The steel connecting rod rode on a caged roller bearing.

The BMW R25/2

The next generation single, the R25, was introduced in 1950. This motorcycle had an all-welded frame to better handle sidecar work and incorporated plunger rear suspension. 1951 saw the introduction of the R25/2, which is what Tony bought. This iteration received a new solo seat suspension system, and a Noris generator, located behind the steel cap at the front of the engine, replaced the Bosch unit found on the R25. The engine now revved out at 5,800rpm, but still made only 12 horsepower. Carburetion was a Bing 1/22/4 or a SAWE K22F.

The front fork is non-hydraulic spring action only, as are the rear plungers. Both wheels are 19 inchers, and the steel rims are painted two-tone silver and black. Half-hub drum brakes of 6.29-inch diameter front and rear provide stopping power. Tipping the scales at 312 pounds fully fueled, the R25/2 can carry double its weight — 660 pounds. BMW claimed a top speed of 65mph.

It proved a hugely popular model, and BMW built 38,651 R25/2s — far outstripping production of twins in the same period — before updating the model with the R25/3 in 1953 (though the R25/2 was still also produced for 1953). That /3 saw an increase in both compression ratio and horsepower, the gas tank was longer and flatter, and both front fork and rear plungers gained hydraulic damping. Hubs changed to a full-width alloy, and rims went from steel to alloy, as well, while shrinking slightly to 18 inches. The /3 was in production until 1956 when it was replaced by the R26 with Earles fork, and finally the R27 of 1960. Although now producing 18 horsepower, the R27 engine was still based on the one first made for the R24. BMW stopped selling its utilitarian single-cylinder motorcycles in 1966. Between 1948 and 1966, BMW built more than 167,000 250 singles.

The natural market for these BMWs would have been well-heeled commuters, but it didn’t take long before European police and postal services — as well as the Red Cross — adopted the single-cylinder BMWs for their use. It’s not clear how many BMW singles were imported to the U.S., but the machines were indeed sold in North America. An ad in the March 1949 issue of The Motorcyclist announced “BMW On the Way Again!” and below the headline was an image of the R24, along with machine details.

Tony’s R25 gets a new life

With the R25/2 in his garage, Tony cleaned the machine as a complete unit. Then, armed with pencil and paper, he began a well-documented disassembly process, pausing along the way to take plenty of digital photographs. Before starting on the project in earnest, the frame was checked to be sure it was straight. It passed, but one slightly tweaked fork tube had to be straightened for reuse. The lower triple clamp was beyond repair, and Tony sourced a used one for replacement.

Tony took the frame, centerstand and sidestands down to bare steel using chemical paint stripper and plenty of elbow grease. He used the same process for the rear brake lever, air cleaner, seat substructure, forks, headlight and headlight mounting ears, and the wheel rims and hubs. Much of Tony’s work was in preparation for powder coating, although he would have preferred single-stage paint. “Powder gives a better result, though, and very even with no runs. I’m very happy with it,” he says, adding, “Today’s standards are different, and the technology of powder is better than paint.” The frame, rear brake lever, centerstand, and hubs and rims were powder coated.

Components such as the fuel tank, headlight bucket and ears, taillight, horn and air cleaner were sent out to Jason LeCavalier in Waukesha, Wis. The pair took photographs, measuring the distance of the pinstripes on the fenders and tank from critical reference points. Then, Jason stripped and prepped the pieces before spraying them black and hand-striping the white lines on the fenders and tank. The original pinstriper at the factory signed underneath these pieces with the initial “R,” so Jason replicated the lettering before laying down clear coat on everything.

BMW usually used either Denfeld or Pagusa rubber saddles, but the seat on Tony’s R25/2 does not have a maker’s mark. Regardless, Tony felt the rubber was in good condition, and he brought it back to life with a silicone cleaner meant for car tires. All the other rubber components, including footpeg covers, grips, knee grips, fuel lines and fork gaiters, were replaced. 

Fresh bearings went in the hubs, and Jason painted the center of the powder-coated rims silver before Tony laced everything together with fresh spokes. The engine was dismantled, and all its components were tagged and bagged. Tony used walnut shell media in a sandblast cabinet to clean and detail the engine and transmission cases, and then left the cases and internals with, as he says, “some deadbeat. I spent a lot of time waiting on the engine before I decided to move on.”

Eventually, Tony retrieved and boxed up the engine, transmission and final drive and shipped them off to BMW specialist Craig Vechorik at Bench Mark Works in Sturgis, Miss. “It was a matter of not having the correct tools to do the work myself,” Tony explains of his decision to send the engine out. Craig found light wear on all the engine’s working surfaces, including the crank and gears. The piston had to be replaced, and the cylinder was bored to the first oversize while the head received new seats and valves.

All of the original BMW fasteners were cleaned on a wire wheel and sent out for cadmium plating. Upon reassembly, Tony made a decision about which replated hardware he would use, and which he would replace with stainless steel. For example, fasteners that might see road grime, such as those located under the fenders, were bagged and inventoried for preservation, and stainless steel replacements found. Tony bought a polishing outfit and polished the Magura hand levers, the suspension covers, steering damper knob, kickstarter, gearshift lever and fork caps. He also polished the tiny aluminum handshift lever — a vestige of the early handshift-only singles. The rear plunger caps and handlebar risers were sent for rechroming.

With the engine and drive components back from Bench Mark Works, Tony installed them in his restored chassis and completed the build with a new exhaust and muffler. It took two years, but in November of 2009 Tony started his R25/2. It wouldn’t idle properly, and it was clear the original SAWE carb wasn’t going to work well, so Tony replaced it with a Bing.

Now, Tony enjoys pottering about on the R25/2 and will occasionally ride the BMW to work. He has friends with scooters and rides the R25/2 with them on longer trips, but he says the machine isn’t cut out for high-speed roadwork. “First gear is very low — I shift out of it almost instantly; I’ll be in second or third gear before I’m across an intersection,” Tony says. “I can do 56mph on a flat surface, but I’ve never really pushed it that hard. It’s not that practical to take into modern traffic, and I can’t take it on the Interstate,” he says with a laugh. So far, Tony’s put about 1,000 miles on the finished bike.

“It was basically a no-expense spared restoration,” Tony says. “But I don’t know any other way of doing things. I might have been able to do just a mechanical rebuild and left the tins alone, but I couldn’t have dealt with the paint loss. What can I say? Like my grandfather and my father, I’m a perfectionist.” MC