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1975 z1 900.From what I seen on the wiring diagram the sending unit grounds itself on the engine block,A single blue wire runs to the oil light.Mine runs off the top of the oil sending unit and into the stator harness which plugs into the fuse box electrical base with the blue connector.Is this where it gets it's positive voltage for the oil light?I checkecked that plug whre the blue wire would connect and there is no power there(top right wire on the stator wire harness plug)At the bulb is blue and brown wires.I assume the brown is ground since it is also connected to the neutral light.Bulb has been switched with a working bulb.Tryig to figure out how the bulb gets it power.Btw,horn works,neutral light works

Blue wire is the ground.
Steve

clarkster wrote: 1975 z1 900.From what I seen on the wiring diagram the sending unit grounds itself on the engine block,A single blue wire runs to the oil light.Mine runs off the top of the oil sending unit and into the stator harness which plugs into the fuse box electrical base with the blue connector.Is this where it gets it's positive voltage for the oil light?I checkecked that plug whre the blue wire would connect and there is no power there(top right wire on the stator wire harness plug)At the bulb is blue and brown wires.I assume the brown is ground since it is also connected to the neutral light.Bulb has been switched with a working bulb.Tryig to figure out how the bulb gets it power.Btw,horn works,neutral light works

Yes, the Clymer diagram is missing the power source for the oil light. Actually, that diagram has a few issues with it. You will probably want to get a factory diagram, or at least a couple other different diagrams to compare with. Another issue is that the diagram incorrectly shows the turn signal wire connected into the oil pressure wire (if you have the same diagram I am using).

The brown wire in the gauge cluster is the power source for the oil light and the neutral light (and stop lamp).
The brown wire is switched + 12v, and is powered up when the ignition switch is turned to run.
That brown wire powers many things on the bike in general.
What looks to be a blue/red wire is the ground wire for the oil light, and that wire goes to the pressure switch.

The solid blue wire in the gauge cluster is 12v power when the headlight switch is on. It powers the illumination lights in the gauge cluster for the tach dial and speedo dial.

I concur on the brown wire being a power source. There is an unused double brown connector coming out of the harness near the headlight that I use to power my Dyna ignition.

I have a large (3 ft by 6 ft) Z1 wiring diagram on my wall for reference. The large size makes it easier for these old eyes to trace circuits and figure things out. It was made with a printer plotter from a PDF file of the wiring diagram in the Z1 manual. I highly recommend a blow up like this if you have access to a printer/plotter.

I followed the wire from the sending unit and it goes through the starter cover into the stator harness.From there it goes to the electrical junction box with the blue connector.So does it run from the junction box and then to the oil pressure light?

Your oil pressure bulb/light get 12 Volt +power, (brown wire), as soon as the ignition switch is in ON Position.
If the engine is not running 12 Volt +power flow through the oil pressure bulb into the blue wire to the closed oil pressure switch to engine ground/negative.
Oil pressure bulb light is on.
As soon as the engine is cranking or running the oil pressure put the oil pressure switch in OFF Position, disconnect from ground/negative.
The oil pressure light gets off.
The oil pressure light switch is an closed not an open switch in the resting state!!!!

Attached photos show the entire Z1 electrical circuit (photo of my wall) and details of the neutral and oil switches. As can be seen in the detail...oil and neutral switches are grounded by the switch.

Edited to add that brown and red are difficult to distinguish from each other...in the manuals and also in my blowup. The brown that I use for powering my Dyna ignition is the double female connector seen just above and slightly to the left of the neutral switch in the diagram. This gives you an idea of how easy it is to mistake brown and red.