and just for the Kawasaki record..
the KX's came out in 1973 with a 125-250 and 450. 1973 was the only year of the 450, as the following year it was a 400.
So a 450 KX is rare in its own right. It also did not have the shiny metal green tank with the white stripe, instead a dull green plastic tank with black lettering only.
like this one a Mid Ohio.
and the pipe was unique to that bike in that it came up and then leveled off at the back.