I think its on the counter shaft, there is a plug in the top of the case just above the sprocket. I saw at least three wires there and usually there is only two wires there for the neutral switch. I could be wrong..
didn't realize there were so many replies to this thread. a friend was testing a rev-limiter delimiter on my bike and i think they had to plug it inline to the 4 plugs location next to the two wire speedo sensor.
there happened to be two 2 wire plugs in that loom and they accidentally plugged them into the wrong female ends, which in turn kept my speedo and odometer from working.
I think the de-limiter was from a Honda PCX, don't know the details on whether it worked or not.
The Stage6 Speedometer measures in at approximately 100mm x 60mm x 20mm and requires a 12V supply from the battery. Revs are picked up inductively while the speed is picked up via a magnet sensor installed at the wheel. Use this to replace your stock speedo for a sleek new digital setup. Available in a variety of colors.