The Solo Rex 125, introduced in 1958 by Solo Kleinmotoren GmbH of Stuttgart, was a powerful one-man chainsaw designed for professional forestry use. It was powered by a 125 cc (7.2 cu in) two-stroke engine producing about 5 horsepower, and weighed approximately 11.4 kg (26 lb) with its standard 17″ guide bar.
The beautifully restored saw featured throughout this article was brought back to life by Alex (eBay: szabsa76), whose craftsmanship and restorations have been highlighted on our blog many times. Alex describes the Solo Rex as his favorite chainsaw—a remarkable endorsement from someone with such deep experience and expertise in vintage saws.
When released, the Solo Rex was groundbreaking as the first European one-man chainsaw to incorporate a diaphragm carburetor, marking a significant leap in portability and fuel consistency across operating positions.
With its 125 cc engine, it outperformed most competing models of the late 1950s and became a benchmark for power in its class. It was also notable for being among the first chainsaws to feature plastic components in its top shell and covers—an early step toward lighter, more ergonomic construction.
Collectors often refer to the Rex’s striking “big blue” styling as both futuristic and monstrous, earning it affectionate nicknames among enthusiasts.
Though heavy and lacking modern safety features, the Solo Rex remains an icon of postwar German engineering—celebrated for its raw power, distinctive design, and pivotal role in the evolution of the modern chainsaw.
| Specification | Details |
|---|---|
| Model | REX |
| Manufactured by | SOLO Kleinmotoren GmbH, Stuttgart, Germany |
| Series or assembly number | 604 |
| Year introduced | 1958 |
| Engine displacement | 7.2 cu. in. (125cc) |
| Number of cylinders | 1 |
| Cylinder bore | 54mm (2.12 in.) |
| Piston stroke | 54mm (2.12 in.) |
| Cylinder type | Aluminum with chrome plated bore |
| Intake method | Piston ported |
| Manufacturer advertised H.P. | 5 DIN, 7 SAE |
| Weight | 26 lbs. (11.4 kg) with 17 in. (43 cm) bar & chain |
| Operator configuration | One man operation |
| Handlebar system | Rigid |
| Chain brake | None |
| Clutch | Centrifugal |
| Drive type | Direct |
| Construction | Die cast magnesium |
| Magneto type | Bosch |
| Carburetor | Tillotson HL-80A |
| Air filter system | Mesh |
| Starter type | SOLO automatic rewind |
| Oil pump | Manual |
| Maximum engine RPM | 4600 |
| Ignition timing | Fixed |
| Breaker point setting | 0.5 mm (0.020 in.) |
| Flywheel/coil air gap | Fixed, not adjustable |
| Spark plug type | Bosch W175, Champion J8J (L10 or L90 normal service; L85 for severe service) |
| Spark plug gap | 0.63 mm (1.025 in.) |
| Crankshaft main bearings | Ball |
| Fuel tank capacity | 1.3 litres |
| Fuel oil ratio | 25:1 |
| Recommended fuel octane | Regular |
| Mix oil specification | SAE 30 or 50 |
| Chain pitch | 7/16″ |
| Chain type | Oregon 62C |
| Shortest guide bar supplied | 43cm (17 in.) |
| Longest guide bar supplied | 75cm (30 in.) |
| Color scheme | SOLO Blue |
Fuel was mixed at 25:1 (gasoline to oil), delivered through a Tillotson HL-80A diaphragm carburetor, while ignition came from a Bosch magneto with fixed timing. The engine had no decompression valve, making it difficult to start and prone to heavy vibration.
Later Rex versions introduced an oval starter pulley to improve cranking leverage. Chain speed was relatively slow compared to modern standards, but the large-displacement engine delivered immense torque, allowing the saw to power through timber by brute force rather than high chain velocity.
We shared the following image on FB with the caption, “The 125cc Solo Rex Chainsaw. Released in 1958 and weighs 26 lbs/11.4 kg.” As someone commented, the image on the left is the Solo 70, with the one on the right being the Rex.
Robert commented, “Had 2 of those beasts. Nothing stopped them.”
To which Jim replied, “You had to get them started first!”
And Robert responded again, “Easy when cold just don’t shut them down and try start it pull your arm off when they kick back.”
Other comments on the post:
- Robbie said, “Back in the days of carpal tunnel and high fatality counts.”
- Steve said, “Dad had one, scared me to death!!!”
- Martin said, “Back when men were men and sheep were very nervous.”
And Michael shared a link to his Double Solo Rex video.
Other Solo saws we’ve featured:
