In addition, BSA had started to manufacture bicycles as well as their spare parts. Following along this trajectory and from 1910 onwards, BSA started to fit its bicycles small single-cylinder engine. Their single-cylinder units varied in capacity as well as a mix of two-stroke and four-stroke combustion philosophies. This was mainly to ensure that the company was covering the diverse needs of the British motorcycle market.
Through its supply of ammunition and their M20 side-valve motorcycles, BSA became also known to have contributed the most (as a manufacturer) to the Allied effort during the Second World War.
Following the end of hostilities in Europe and elsewhere, the company acquired Ariel and Sunbeam, and also started to manufacture two-cylinder inline engines. It was also around about this time that BSA branched into the manufacture of scooters.
The 1960s went reasonably well for BSA. However, with the appearance of Japanese motorcycles on the American market—the main source of BSA’s customers, the company was forced into bankruptcy, despite intervention from the British government.
The S25, also known as Modelo S25 or the “Sloper”, was purchased in 1964 at the BSA dealership in Viseu, by A. Henriques. The bike was purchased for the sum of $850 and the engine was rebuilt at Ed. Ferreirinha in Porto. It was later donated to the Museu do Caramulo by Pedro Corrêa de Barros.