Hi chaps, I am trying to wire up a tacho which came from a different bike on my race bike.
It is reading up to 9,000 RPM but should read around 14,000. It is wired from the negative side of the coil with a 12v DC input and earth. Obviously the tach works from a pulse. Inside the clock it has a varible resistor, when adjusted to max it reads what I have mentioned above.

Here is my question.... If I took a secondry negative wire from the other coil would this double the output? Or would I blow up my coils? I don't want to try this until certain that this can be done? Help appreciated.