[johndeereelfman]

Here are the 400 series serial number breakdowns.

400 Serial Numbers:

1975 =   30,001 -   55,000 (19.9hp Kohler Engines)

1976 =   55,001 -   70,000 (19.9hp Kohler Engines)

1977 =   70,001 -   80,000 (19.9hp Kohler Engines)

1978 =   80,001 -   95,000 (19.9hp Kohler Engines)

1979 =   95,001 - 120,000 (19.9hp Kohler Engines)

1980 = 120,001 - 155,000 (19.9hp Kohler Engines)

1981 = 155,001 - 190,000 (19.9hp Kohler Engines)

1982 = 190,001 - 222,000 (19.9hp Kohler Engines)

420 Serial Numbers:

1983 = 222,001 - 285,000 (20hp Onan Engines)

1984 = 285,001 - 315,000 (20hp Onan Engines)

1985 = 315,001 - 360,000 (20hp Onan Engines)

1986 = 360,001 - 420,000 (20hp Onan Engines)

1987 = 420,001 - 475,000 (20hp Onan Engines)

1988 = 475,001 - 595,000 (20hp Onan Engines)

1989 = 595,001 - 999,999 (20hp Onan Engines)

1990 = 010,001 - 100,000 (20hp Onan Engines)

1991 = 100,001 - 110,000 (20hp Onan Engines)

1992 = 110,000 - 120,000 (20hp Onan Engines)

430 Serial Numbers:

1984 = 285,001 - 315,000 (20hp Diesel Yanmar Engines)

1985 = 315,001 - 360,000 (20hp Diesel Yanmar Engines)

1986 = 360,001 - 420,000 (20hp Diesel Yanmar Engines)

1987 = 420,001 - 475,000 (20hp Diesel Yanmar Engines)

1988 = 475,001 - 595,000 (20hp Diesel Yanmar Engines)

1989 = 595,001 - 999,999 (20hp Diesel Yanmar Engines)

1990 = 010,001 - 100,000 (20hp Diesel Yanmar Engines)

1991 = 100,001 - 110,000 (20hp Diesel Yanmar Engines)

1992 = 110,001 - 120,000 (20hp Diesel Yanmar Engines)