The Japanese Big Four are the large motorcycle manufacturing companies of Japan:[1][2][3]
This model was Yamaha's first motorcycle and the starting point for Yamaha Motor Co. Ltd.
Competitive engines are manufactured by the big four Japanese companies: Honda, Kawasaki, Suzuki, and Yamaha.
The enactment of the import tariff ... hasn't kept the two sides -- Harley-Davidson and Japan's Big Four manufacturers--from talking to each other... [Harley has] met with representatives of Honda, Yamaha, Suzuki and Kawasaki to discuss possible alternatives to the tariff.