In 1980 the first major upgrading of the 750cc and 1000cc machines with 16-valve (four valves per cylinder) heads with the valves being actuated though short forked rockers, and the enlargement of the litre bike to 1100cc (actually 1074cc). The new heads incorporated Suzuki's Twin Swirl Combustion Chamber (TSCC) technology and machines sporting the new technology were designated as GSX models in Japan, Europe, Africa, Australia, New Zealand, and many other markets, differentiating them from their two-valve per cylinder stable mates. In the Americas the GS code continued to be used for both four and two valve per cylinder machines. The 750 engine also received a plain bearing crankshaft and higher geared oil pump to increase oil pressure to the crank. The 8-valve 650cc engine (actually 673cc) also got plain bearings and marked the transition from two-stroke origins of the design and facilitated the move to air-oil cooling. The introduction of air-oil cooling via large radiators known as SACS in the road-going Suzuki motorcycle demarcated the GS/GSX machines from the new technology of the GSX-R machines, however this distinction is blurred somewhat by later models such as the GS1200SS which used the SACS equipped GSF1200 Bandit engine. During the 1970s and early 1980s the GS-range of models and contemporary machines from other Japanese manufactures shared so many common design configurations and features that this commonality of design gained the moniker the Universal Japanese Motorcycle. The universality of design wasn't that surprising as the GS and its contemporaries were designed as 'general purposes motorcycles' capable of sport riding, touring and commuting. It wasn't until the further development of more purpose-specialized machines, beginning in the GS range with the shaft-drive models for touring and the more sports-oriented GS1000S and GS/GSX1100 Katana models and later fully faired touring machines and race-replicas. The range of motorcycles in the series had engine displacements between 125 cc and 1150 cc, and include the GS400 and GS500. The GS series also include the original Katana series, although both the 1000 and the 1100 had 16 valves, thus being a GSX. It was however still designated as a GS on some markets, primarily in the US. The G suffix after the model number indicates the model uses a shaft drive instead of the chain drive system. The G models included the GS650G and GL, GS750G and GL, GS850G and GL, GS1000G and GL, and GS1100G, GK, and GL.