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Yamaha XS1 XSB XS2 TX650

The Yamaha XS1, XSB, XS2, and TX650 motorcycles were a series of shaft-driven, parallel-twin motorcycles produced by Yamaha from 1970 to 1984. The XS1 was the first model in the series, introduced in 1970. It was a 650 cc (39.7 cu in) motorcycle with a single overhead camshaft (SOHC) engine. The XSB was a slightly detuned version of the XS1, introduced in 1972. It had a lower compression ratio and less horsepower than the XS1. The XS2 was a more powerful version of the XS1, introduced in 1973. It had a higher compression ratio and more horsepower than the XS1. The TX650 was a touring version of the XS2, introduced in 1975. It had a larger fuel tank, a more comfortable seat, and a fairing.

All four models were powered by a 650 cc (39.7 cu in) parallel-twin engine. The engine was air-cooled and had a SOHC design. The XS1 and XS2 had a compression ratio of 9.2:1, while the XSB had a compression ratio of 8.5:1. The TX650 had a compression ratio of 9.5:1. All four models had a bore and stroke of 75 mm × 56 mm (2.95 in × 2.20 in).

The XS1, XSB, XS2, and TX650 all had a five-speed transmission. The XS1 and XS2 had a chain final drive, while the XSB and TX650 had a shaft final drive. The XS1 and XS2 had a wet weight of 440 lb (200 kg), while the XSB and TX650 had a wet weight of 450 lb (205 kg).

The XS1, XSB, XS2, and TX650 were all discontinued in 1984. They were replaced by the Yamaha XJ650, a more modern motorcycle with a DOHC engine and a chain final drive.