On the back of the twin cam/6 dial dash, the tacho has 2 connections. One tab (power) and the other, in my case is a singe white wire going through some kind of clip with a screw fitting on it. So by all accounts there are two white wires coming out of it.
But...the white wire is one single strand, with 2 ends, threaded through the clip.

When i connected my wires form my old external tacho, the engine wont start, and i'm guessing i'm creating a loop as the white tacho wire is only one thread...

Does anyone understand what i'm talking about, and how the white piece of wire works?

Ta, Alex

You guessed correctly. The white wire loops from the distributor points through the tacho clip to the coil. The clip on the tacho detects the magnetic field generated by the pulsing current which in turn drives the tacho. The higher the revs the bigger the magnetic field. I've found that the type and age of wire and insulator makes a huge difference to the tacho stability. If it doesn't work the first time try replacing the length from points to coil.

Cheers
Brett.

cool. so what goes on each end of the white wire? neg and pos coil?

A

The distributor points switch the coil to ground so you want one end on the coil -ve and the other on the distributor points fly lead. The +ve side of the coil goes to ignition and from memory and second wire from the starter.

Cheers
Brett.

If you look under the dash, there will be a white (or black) wire with 2 bullet connections, undo these and they go to the tacho. Easy.

Here is a diagram if you need any help....

http://media.turbosport.co.uk/2005/3/8693238200503040701.gif

Shaun