The GSX Series is Suzuki's range of sport touring motorcycles powered by four-valve per cylinder four-stroke engines. The first GSX models were introduced in 1980 and represented the next step in Suzuki's four-stroke road bike range after the two-valve GS Series. In North America though, the Suzuki four-valve and two-valve four-stroke road bikes were both designated as Suzuki GS motorcycles. The two-valve engines remained in production in parallel with the four-valve power plants, the larger two-valve four-cylinder engines gaining shaft-drive and being used to power Suzuki's more touring-orientated bikes such as the GS 850G and GS 1100G, while the GSX series represented performance orientation. GSX Development The two-valve GS Series was Suzuki's first real foray into four-stroke motorcycles. Although Suzuki produced 90cc and 123cc four-stroke single cylinder road bikes under the brand Colleda in the mid-1950s, up until 1976 Suzuki was primarily a builder of two-stroke motorcycles. Suzuki's range of road going motorcycles was almost entirely two-stroke in the mid-1970s (the oddball being the Wankel Rotary powered RE-5). The sophisticated Suzuki GT series and the flagship 750cc water-cooled, posi-lube lubricated, three-cylinder two-stroke GT750 characterizing the breed. The GS750 introduced in 1976, along with the parallel-twin GS400, was Suzuki's first large multi-cylinder four-stroke motorcycle. The GS was Suzuki's version of what was and is referred to as a Universal Japanese Motorcycle, so common was this 4-cylinder four-stroke configuration amongst the Japanese manufacturers at the time. The 63 bhp air-cooled, twin-cam, in-line four cylinder, GS750 road bike set the pattern for the GS/GSX range until the birth of the first of the race-replicas, the 1985 air/oil-cooled Suzuki GSX-R750. The GS750 two-valve engine showed the influence of Suzuki's long history of two-stroke design and manufacture; the new four-strokes sporting pressed together roller bearing crank-shafts universally used in two-stroke bottom ends. Twin Swirl Combustion Chamber (TSCC) The key feature of the GSX engine was the change from the common two-valve per cylinder hemispherical combustion chamber with domed piston design of the GS engine, to a four-valve per cylinder Twin Swirl Combustion Chamber (TSCC) with flat topped piston design. The TSCC design was essentially a modification of the Pent-roof combustion chamber design to which was added a slightly raised ridge running along the combustion chamber roof parallel to the gas flow of the inlet charge. This was to encourage controlled swirl of the incoming fuel-air charge in order to increase the fuel burn speed through