Speedometer Kph to Mph

Hi all, I have a Monster 1000s ie, it was imported from Japan a few years ago. I changed the instrument cluster from the Kph original to a new Mph dash. All works except, the speedometer is still showing Kph. When I doing 50, its showing 80 etc. And the odometer is recording kilometres not mile.
Is there a procedure for changing the instrument cluster from Kph to Mph and if so, does anyone know how its done please?
Thanks