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Yamaha entered the ATC market in 1980, after paying patent-right to Honda to produce their own version of the All Terrain Cycle. Starting modestly with a 125cc recreational ATC that would remain the foundation of their line through 1985, the YT125 featured a 2 stoke engine with sealed airbox with snorkel intake, an autolube oil injection system, and featured a narrow tunnel above the engine that was advertised to make the machine easier to keep stable in precarious situations. Advertising pointed out the durability of the tires, at a time when Honda ATC's were still known for relatively weak low-pressure balloon tires.
Yamaha followed the YT125 with the introduction of the YT175 in 1982.