speedo repair
 

hi folks does anyone know if you can dismantle a speedo (1vj) because the one on my bike is in kph and the trip button/knob doesnt work .
also i have got another speedo from another bike with mph reading but the outer casing is very tatty looking and the trip button/knob is missing so i would like to make a good one from the two. another thing i would like to know if anyone knows is the speedo drive the same ratio on the wheel for both kph/mph .

My Speedo on my 89 TX600 was reading 15-20 MPG too fast. I was able to open it up and bend the spring arm support but it's not quie enough. The housing is glued onto the base, I was able to separate it with a putty knife.
I wondered about those KPH/MPH drives too.
Steve