Speedometer gearing?

I'm looking for a different speedo for my GN125 and was wondering where I could find the gearing or ratio of my current speedo. If I could ballpark it that would be close enough, I could calibrate it with my GPS and draw up a new face.

most japanese bikes have a 1:1,4 ration, so most speedos will fit

Most Japanese bikes are a 2:1 ratio.

Thanks guys, should be close enough. I got one that goes to 140 kph and since I don't expect to go much over 100 on my 125 that should give me some headroom for calibrating it with a new faceplate. Wanted one without a trip-meter and pilot lights anyway, so the 10 bucks won't hurt if everything goes wrong.