Originally Posted by ailgup
i tried the ferrite bead and it would fork about 10% of the time, but it had to be held out away from wires especially the kill switch wire. I was wondering if it could be coming from the kill switch but i saw in Earthman's bike the kill switch wire was close to the other wire and it had no problem. also i will try but how would you replace the wire i could find no way to open the CDI box it seemed molded shut???
Don't try to open the DCI. It is sealed and doesn't need to be opened. The sparkplug wire can be removed by unscrewing it - twist it CCW. Screw the new wire in by turning it CW into the CDI.
The ferrite bead works best if the wire makes 2 or 3 loops through it. Just make a little coil of wire and snap the bead on all the loops. Keep the bead as close to the speedometer head as possible. Put 2 or 3 beads on if necessary.
Make sure the contacts between the speedometer and the handlebar mount are clean, and there is good contact. If the speedometer works when the engine is off, you are probably ok.
If the better sparkplug wire and beads don't work, you could try shielding the sensor wire. If all three don't work, you have a poorly designed speedometer - buy a different brand.