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1972 Yamaha DS7
The Yamaha DS7 motorcycle was made in 1972 for one year. It was a 250cc twin two-stroke that made 30 hp @ 7,500 rpm. Top speed was 93 mph. 12v battery ignition. five-speed gearbox. 1/4 mile in 14.8 seconds.
The DS7 was the initial forerunner of the Yamaha RD series of motorcycles started in 1973. The major difference between the 250 cc DS7 and 350 cc R5 of 1972 and the 1973 RD250 and RD350 was that the DS7 and R5 utilized piston-port induction, whereas the RDs were introduced with reed valve induction.
The 250 was "oil injected" meaning that although the 250 was a 2 stroke or (2 cycle engine) there was no need to premix the gas and oil. The gas tank only contained gas but the oil was injected from an oil tank beneath the seat.