BODYWORK. Frame: steel tube monocoque. Front suspension: link fork. Rear suspension: rigid.

MECHANICS. Engine no.: 4307219. Engine: single-cylinder, two-stroke. Displacement: 63 cc. Transmission: by friction roller. Gearbox: 2-speed.

DOCUMENTS: No documentation, but registered under plate number 5047 Sitges.

HISTORY: Despite its modest power, the auxiliary engine powering this bicycle represents a fascinating chapter in the history of the Spanishmotor industry. Produced between 1953 and 1960, it had limited commercial success due to the rise of the SEAT 600, which overshadowed theentire two-wheeler sector. However, its manufacturer, Construcciones Mecánicas Rex, was one of the oldest in Spain, having started operations in 1913 under another name, initially producing industrial engines.

Two years later, the company hired a young and promising engineer named Wifredo Ricart, who would go on to achieve a brilliant career — mostnotably with Pegaso. In 1953, long after leaving the company, Ricart designed this small inverted-cylinder engine for Rex, with the fuel tank and exhaust silencer integrated into a single unit. Mounted above the rear wheel, it transmits power to the tyre via a friction roller. Featuring flywheelmagneto ignition and a proprietary carburettor, it delivers 1.2 hp, allowing a top speed of 45 km/h with a fuel consumption of just 1.8 litres per 100 km.

The example offered here corresponds to the second version of the model, equipped with a sturdier moped-type frame instead of a bicycle frame, and even front suspension. It was carefully restored by its previous owner, who had begun his professional career as an apprentice mechanicat Construcciones Mecánicas Rex.