Yamaha Merken Yamaha Xs 400 dohc reduced effect Yamaha Xs 400 dohc reduced effect generaties Yamaha Xs 400 dohc reduced effect 1982 Yamaha Xs 400 dohc reduced effect 1983 Yamaha Xs 400 dohc reduced effect 1984 Yamaha Xs 400 dohc reduced effect 1985 Yamaha Xs 400 dohc reduced effect 1986 Yamaha Xs 400 dohc reduced effect 1987 Yamaha Xs 400 dohc reduced effect 1988