Well, after quite a few hours head scratching and pulling wires out, I've finally worked out that the ECU tacho signal output is non existant. The original ETB tacho picks up a signal from the Fireblade ECU (919 carbed model, so ECU does timing/ignition only) which output a signal for 4 cylinders. I've tried the tacho using a signal from one coil pack (which runs 2 cylinders) and it responds, but only at half speed obviously. I've got no way of changing the ETB tacho (there are no user settings as it was specifically for the factory built model).
Could I splice in two signal wires, one from each coil pack, and join them together feeding the tacho? If I fit a diode in each signal wire to stop any back feeds to the opposite coil? Would this work or am I talking a load of rubbish???
