Some great comments there guys, I feel much more the wiser and now understand it all more. I shall give suggestions a go tomoz.

Because the tacho is off another model, then it may be possible that its set for a different kind of pulse from the CDI and not that of a CBR. The tacho was from a VFR which is a V4?
I will let you all know of my findings. Who ever messed with the current wiring loom needs shooting! Thanks again. I determined to beat this problem lol.

Ok, I have checked the pulse wire from the CDI, on idle it's putting out 1.5V but when you rev the engine it goes up accordingly, the most I saw was 5.5V?

Next I will try wiring it up on LT side of the coil. I did try this before but will try the other coil. It did read last time out but only about a 1/4 of revs it should be reading.

Have you tried contacting the manufacturer and asking for the technical data so you can at least know what you're looking for?

I guess I could call the local dealer and ask. I wish I had the standard tacho just to clear up a few things or a donor CBR600 for cross reference.

I have a hunch that the tacho is dead. I fitted my old mini electronic tacho to the yellow & green pulse wire from the CDI and the tacho worked fine from there. So it must be the tacho. I will buy another set of CBR clocks from fleabay, maybe the 900 fireblade ones will work.

Told ya so. :icon_couchhide:

I'm not eating humble pie just yet, and new tacho will tell the tale. If it's the old tacho I will throw it as far down the road as possible. I have spent days trying to diagnose this problem lol.

Just bought another set of VFR400 clocks from fleabay. I will try them without taken them to bits this time. If they do not work at least I can throw them back on!

Well wired up the new set of clocks and guess what? Nothing again. The needle does not move at arrrrragggghhhhh.
I have studied both manuals the VFR & the CBR. My findings were for the CBR;
The tacho only appears to have two wires. Yellow & Green (CDI Pulse) and green (earth) and no live 12V DC wire?

The tacho on the VFR has 3 wires, Yellow & Green (CDI Pulse) Green (Earth) & Brown & Black (Live 12V DC)

I'm gonna try one more thing... I will try wiring the pulse wire from the tacho to each terminal of the coil. One of the four terminals has to work???