MotoSpecs

1951 BMW R 25/2 Specifications

All-Round • Specs last verified 31 October 2026

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1951 BMW R 25/2 Overview

The 1951 BMW R 25/2 is an all-round motorcycle built around 247 cc of displacement. Under the tank sits a Four stroke, single cylinder, pushrod operated, OHV, 2 valves per cylinder engine, a compression ratio of 6.5:1. 1951 BMW R 25/2 delivers 8.9 kW @ 5600 rpm of peak power. From a practical standpoint, the 1951 R 25/2 tips the scales at 142 Kg and carries a 12 L fuel tank. That's roughly 47 kg lighter than the average all-round motorcycle in our database. Scroll down for the complete 1951 BMW R 25/2 spec sheet covering every technical detail from suspension travel to tyre sizes.

1951 BMW R 25/2 compared with other bikes in the All-Round category

Here is how the 1951 BMW R 25/2 stacks up against other bikes in the All-Round category in our database. Each model counts once, using the model year closest to this one, and the comparison covers up to 381 models.

  • Power-to-weight ratio of 63 W/kg is lower than that of 127 of the other 135 bikes in the All-Round category.
  • Only 15 of the other 145 bikes in the All-Round category have a lower power output than the 8.9 kW of the R 25/2.
  • With 142 kg, the R 25/2 has the joint 84th lightest wet weight of 381 bikes in the All-Round category, 25% below the category average of 189 kg.
  • Narrowing the field to the 11 models within five model years of it, the power-to-weight ratio of 63 W/kg is lower than that of every one of the other 10.

1951 R 25/2 - Pros & Cons

Strengths

  • Capable power output: At 8.9 kW @ 5600 rpm, the R 25/2 holds its own against class rivals.
  • Low-maintenance final drive: Shaft final drive means no chain to clean, lube or adjust - meaningfully less routine maintenance than a chain-driven equivalent.

Considerations

  • Drum rear brake: The drum rear brake is adequate but lacks the modulation and fade resistance of a disc setup found on more modern equivalents.
  • Modest fuel capacity: The 12 L tank means more frequent fuel stops on longer rides, which is worth planning around on touring routes.

Wear Points & Servicing Notes

Heat management in traffic

R 25/2's air-cooled design means engine-bay temperatures build up more in stop-start traffic than on a liquid-cooled equivalent - a function of the cooling method itself, not a defect. Mesh riding gear and avoiding prolonged idling help in hot climates.

Suspension condition on used examples

Up front, the R 25/2 runs Telescopic fork and Pushrod suspension, spring loaded saddle at the rear. On a used example, check fork seals for weeping oil and test the rear linkage for play - seals are a relatively cheap fix but useful when negotiating price.

Final drive maintenance

Final drive is by shaft - no chain or belt maintenance at all, though the drive-shaft oil should be changed on the manufacturer's interval.

Frame & chassis check

The frame is Closed steel twin loop frame, welded - worth a visual check for corrosion or impact damage around the head-stock and swingarm pivot on any used example, since frame damage is far costlier to fix than any service item.

R 25/2 - Buying & Maintenance Guide

What to check before buying

When inspecting a used 1951 BMW R 25/2 with its 247 cc all-round, start with the basics: check the service book for oil change frequency, inspect the drivetrain for wear, and look for oil seepage around the engine casings and rocker covers. This model runs shaft final drive, so ask for proof the shaft-drive gear oil has been changed on schedule - it's easy to overlook since there's no chain to draw attention to it. Now 75 years old, this all-round is as likely to show age-related wear (perished rubber, seized fasteners, degraded seals) as mileage-related wear. A cold start test is invaluable - a well-maintained R 25/2 should fire up cleanly and settle to a smooth idle within a few seconds.

Oil and filter changes

Regular oil changes are the single most important maintenance task for the R 25/2's 247 cc four stroke, single cylinder, pushrod operated, ohv, 2 valves per cylinder.. Stick to the manufacturer's interval - typically every 6,000 km or once a year, whichever comes first. With a 6.5:1 compression ratio, running the octane grade specified in the manual matters more than on a lower-compression engine. Always use the correct viscosity grade as specified in the owner's manual.

Carburetor upkeep

Keep the carburetors clean and free of deposits. If the R 25/2 has been stored, strip and clean the carb float bowls before attempting to start it. Pilot jets are the first to block and the last to be checked - always include them in any carb rebuild.

1951 BMW R 25/2 - Frequently Asked Questions

What engine does the 1951 BMW R 25/2 have?
The 1951 BMW R 25/2 uses a Four stroke, single cylinder, pushrod operated, OHV, 2 valves per cylinder. engine with 247 cc of displacement. It is air cooled.
How much does the 1951 BMW R 25/2 weigh?
The 1951 BMW R 25/2 weighs 142 Kg. This is the manufacturer's wet figure.
How much power does the 1951 BMW R 25/2 make?
The 1951 BMW R 25/2 produces 8.9 kW @ 5600 rpm of power.
What is the fuel tank capacity of the 1951 BMW R 25/2?
The 1951 BMW R 25/2 has a 12 L fuel tank. At around 5-6 litres per 100 km, that is roughly 200-240 km between stops.
What brakes does the 1951 BMW R 25/2 have?
The 1951 BMW R 25/2 uses ∅160mm Drum at the front and ∅160mm Drum at the rear.
What tyre sizes does the 1951 BMW R 25/2 use?
The 1951 BMW R 25/2 runs 3 x 19" front and 3.25 x 19" rear tyres. A good selection of sport, touring and all-weather rubber is available in these sizes.
What gearbox does the 1951 BMW R 25/2 have?
The 1951 BMW R 25/2 is fitted with a 4 Speed transmission.

Key Specifications

Engine

Four stroke, single cylinder, pushrod operated, OHV, 2 valves per cylinder.

Power

8.9 kW / 12 hp @ 5600 rpm

Torque

Not recorded

Top Speed

Not recorded

Weight

142 Kg / 312 lbs

Fuel Capacity

12 L / 3.1 US gal

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Full 1951 BMW R 25/2 Specifications

Year 1951 - 53
Make BMW
Model R 25/2
Make Model BMW R 25/2
Fuel Capacity 12 L / 3.1 US gal
Oil Capacity 1.25 litres
Wet Weight 142 Kg / 312 lbs
Maximum RPM 5600 RPM
Max Power 8.9 kW / 12 hp @ 5600 rpm
Stroke 68.0 mm
Displacement 247 cc / 15.1 cu in.
Engine Detail Four stroke, single cylinder, pushrod operated, OHV, 2 valves per cylinder.
Bore x Stroke 68 x 68 mm
Compression Ratio 6.5:1
Cooling System Air cooled
Fuel Induction 1x Bing type 1/22/44 or SAWE type K22F
Ignition Battery ignition
Starter Kick
Clutch Single plate, dry
Final Drive Shaft
Gear Ratios 1st 6.10 / 2nd 3.00 / 3rd 2.04 / 4th 1.54:1
Transmission / Drive 4 Speed
Frame Type Closed steel twin loop frame, welded
Suspension - Front Telescopic fork
Suspension - Rear Pushrod suspension, spring loaded saddle
Tachometer None
Brakes - Front Diameter (in.) 6.3 in
Brakes - Front Diameter (mm) 160 mm
Brakes - Rear Diameter (in.) 6.3 in
Brakes - Rear Diameter (mm) 160 mm
Brakes - Front ∅160mm Drum
Brakes - Rear ∅160mm Drum
Tyres - Front 3.00 x 19"
Tyres - Rear 3.25 x 19"

Specifications are compiled from manufacturer documentation and cross-referenced technical sources, and corrected on an ongoing basis. Spot an error? Let us know.

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