Bührer BG4
Built: 1937–1942 · Series: B
More machines from model year 1937
Bührer BG4: four-cylinder tractor of the B range with a wood-gas option, 50 hp, 1,600 kg unladen weight, built 1937 to 1942
Bührer, a Swiss tractor maker based in Hinwil in the canton of Zurich, was among the early makers of field tractors developed and built in Switzerland. The BG4 in the B range was built from 1937 to 1942, in the years immediately before and during the Second World War.
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The BG4 carries a water-cooled four-cylinder engine of 3,285 cm³ displacement with rear-wheel drive, running on petrol, low-grade petrol or wood gas, producing 50 hp; a 4V-1R gearbox provides four forward and one reverse gear. With an unladen weight of 1,600 kg, the BG4 was built for the mid-sized Swiss farms of its day, for tillage and everyday draft work around the farmyard.
The wood-gas option reflects the fuel shortages of the war years, when Switzerland was largely cut off from oil imports by the Allied and German economic blockade: an onboard generator produced combustible gas from wood or charcoal to run the petrol engine instead of petrol itself. This conversion was common in Swiss farm machinery and vehicles during the war.
When buying such an old model second-hand, the condition of the engine and carburettor, the tightness of the cooling system, and rust on the sheet-metal parts and chassis matter. If a wood-gas generator survives with the vehicle, its condition further decides the vehicle's museum value, since matching components are no longer made and originality is what collectors look for.
Sources: SpecCodex-Register: Kennwerte des Modells Bührer BG4
Technical data
Engine
| Fuel | Benzin/Petrol/Holzgascorrect |
|---|---|
| Power | 50 hpcorrect |
| Power | 50 hpcorrect |
| Cylinders | 4correct |
| Displacement | 3,285 cm³correct |
| Cooling | water-cooledcorrect |
Dimensions and weights
| Unladen weight | 1,600 kgcorrect |
|---|
Drivetrain and chassis
| Drive | rear-wheel drivecorrect |
|---|---|
| Gearbox | 4V 1Rcorrect |
| Forward gears | 3correct |
Where this model stands
Power-to-weight ratio: 23 kW/t (37 kW / 1.6 t)
Power class: Universal (40–100 hp)
Stronger than 34% of the tractors in the register — out of 15,663 models with a stated power figure.
Calculated from the documented figures above — not a rating.
Frequently asked questions
How much power does the Bührer BG4 have?
The Bührer BG4 delivers 50 hp.
How much does the Bührer BG4 weigh?
The unladen weight is 1,600 kg.
What engine does the Bührer BG4 have?
4 cylinders, 3,285 cm³ displacement, Benzin/Petrol/Holzgas.
When was the Bührer BG4 built?
Production years: 1937–1942.
What to check before buying
- Check the hour meter against the service records — a replaced instrument is the most common gap.
- Compare the data plate and chassis number with the papers.
- Check the weights in the papers against the figures here — attachments change them.
- Shift the gearbox cold and warm — jumps only show up at temperature.
- Load the hydraulics and watch for sag.
- Ask about parts availability for this build year — the running costs hang on it.
A general list for this type of machine — no substitute for an inspection or an appraiser.
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This page carries 10 individual figures for this model. They come from 2 recorded sources; every figure can be traced there. What we cannot document is not here — we leave gaps open rather than estimate them.
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Tractor in 3D section
Turn the model, look inside and click an assembly — each one is explained.