Rev counter wiring

[GroovyCarrot]

I've got an aftermarket rev counter sitting in the shed.. not sure if I actually want to fit it but I would like to see if it works at least. Problem is I don't know how to wire it up. There are four wires, I think they were black, red, brown and green although I haven't checked so that might be wrong. Anyone know how to do it?

[ste mk1lx]

should be pritty straight forward to wire up

at a guess, so its not my fault if it blows up

red = batt positive
black = negative
green = coil trigger trace, can't remember which coil terminal
brown = illumination