hi the 85 kx500 is a great bike
it was designed by kent howerton
and was made small in size
no power valve the fastest standard 500 made 40 mm carb boost bottle mmmmm
no real problems except the shock rocker arm
was prone to breaking
i broke one in 1985
and i broke one last year leading a vets race on her
racing against all the modern 4 strokers
they are fairley rare over here only 35 were imported to australia
i think ther are quite a few in the usa