1954 BMW R25/3

The 250cc 1948 R24 single, photo below left, was BMW's first postwar motorcycle and the only postwar BMW motorcycle without a rear suspension. Click here to read about the R24.

The 1951 250cc R25 single, photo below right, was BMW's first postwar single-cylinder motorcycle with a rear suspension. Notice the small rubber gaiters above the front axle and the tool box on top of the tank.

 

With the 1953-to-1956 R25/3, BMW updated the 250cc OHV single with a new hydraulic fork, a gas tank that was flatter and longer, with the tool box moved to the side, and different wheels and hubs. Rims were changed from steel to alloy, and shrank to 18” from 19”. Engine configuration specifications changed slightly. The compression ratio went from 6.5:1 to 7.0:1, and power was increased from 12 HP to 13 HP.

The R25 series were very popular BMW motorcycles. There were 47,700 were sold over three years, compared to 12,020 R24s, 23,400 R25s, and 38,651 R25/2s (photo above).

In the photos below is a 1954 R25/3, the last year of the R25 series of motorcycles. Note the full-width brakes, front fork sliders, air pump, chromed front fender backet, and longer gasoline tank, under which resides the air cleaner. Also, the seat suspension spring has changed. Click here to read the R25/3 specifications.

Clearly, BMW AG was proud of the changes from the R25/2 to the R25/3, as noted on page 7 of the 1955 owner's manual:

“The R25/3 has been developed from the well-proven R25/2 design. Its engine unit, being now rubber-mounted in the frame, provides increased output and in spite of this the exhaust noise could be reduced in a still more efficient way, such as it is required for modern traffic conditions. This improvement will be highly appreciated by all road users, particularly when accompanied by gentle driving manners, which mark the true motorcyclist. Riding qualities are improved through smoother wheel suspensions including double-acting oil dampers in the front forks. The 18-inch wheels have light-alloy [aluminum] rims and enlarged braking areas. The tail lamp body incorporates a stop light connected to the foot brake, which is mostly used in town traffic.

“In order to obtain sleeker tank contours, the tool box has been transferred to the left-hand side, where it forms a recess behind the rubber knee pad, which arrangement permits a luggage carrier to be mounted upon the petrol [gasoline] tank.”

In late 2011 and early 2012 Craig Vechorik and his crew at Bench Mark Works went through the engine, electrics, transmission, fuel tank, rear drive (replaced the sidecar ratio rear drive with a solo version), and front end to restore everthing to as-new condition. These photos show the R25/3, albeit a little dust covered, after it was returned. Now it runs beautifully and has a side stand, mirrors, and horn it did not have before.

All that remains now is to recalibrate the MPH speedometer from its current W=2.0 sidecar ratio to the W=1.6 solo ratio. Happily, North Hollywood Speedometer can do that for me.

The three pages below were scanned from BMW's 1954 sales brochure.

The pages below are technical pages from the 1955 R25/3 Handbook. Here is the entire handbook in German (PDF file).

The wiring diagram below is from Doug Rinckes' excellent book, “BMW /2 Electrics.” If you are working on an R25/3 or any /2, you should have this book. It may be purchased from Bench Mark Works.

The exploded engine diagram below is from the 1954 R25/3 Ersatzteilliste.

Click here for R25/3 specifications

Click here for the 1953 BMW R25/3 owners manual.

Click here for the 1966 BMW R27 owners manual.