89 R100 GSPD Wiring diagram problems
 

I've just got an 89 R100 GSPD with about 50 k miles. I think this bike started life as a R100GS and got inself converted to a PD via a dealer installed kit. From what I can see, wiring diagrams for 89 GSPDs are thin on the ground and I've been making do with a GS diagram and marking it up.

I've been tidying up some of the elctric wiring around the instrument area and have run into a problem with the tacho. When I removed the tacho I neglected to photograph the connecting wires and may have put them back incorrectly. At first the tacho registered about double the rpm now it goes instantly to full scale deflection. The 3 tacho connections are marked with Z, +, -. I connected the line from the ignition unit to Z, the power line to + and the grounded line to -. Does anyone know it this is correct or have any other thoughts?? I guess the I might have cooked the tacho.

Thanks in advance for your help

I'm not sure about the markings on the GS-tacho, but:

Black (from coil, Z/DZ)
Brown (Ground)
Green/Black (12V, when ignition is on and killswitch okay)

The ground is shared with all other cocpit-lights.