75 kz400d neutral light issue. Help needed!

I have a kz400d I am rebuilding and cannot get the neutral light to light up. I have replaced the wiring with a universal wiring harness and I have a ricks regulator rectifier on the bike. I can get the oil light to light up I can get the headlight to turn on and the headlight indicator for hibeam. I have confirmed that the neutral light is not blown out and the wiring from the neutral to the neutral light is good. If I disconnect the neutral light from the connection it's supposed to go to and touch it to the ground ,it lights up this is in the headlight bucket. This was working at one point and I cannot figure out what the issue is. I have made this a kickstart only bike and eliminated the starter motor and the starter chain. Any ideas, last night I pulled out the neutral switch and tested it and it seems to be OK from what I can tell. Any help would be appreciated.

I'm not familiar with the kz400 but the wiring diagram shows it to be the usual simple circuit.
When ignition is on, power goes from ignition switch to neurtal indicator bulb to neutral switch which is activated when it is grounded and the circuit is completed lighting up the bulb.
With a multimeter check for 12V at the bulb holder. Usually the brown wire in the bottom center of the bulb holder. You tested the bulb so next pull the wire at the neutral switch off the switch and test if have you continuity/ resistance between the bulb holder and the connector which connects to the neutral switch . Have you 12 volts here between the connector and the engine casing?. The bulb should light if you ground this wire to the engine case.

You should only need to look at connections in the headlight bucket if you are tracing a break or short.

If all checks out . No shorts no breaks then the only things left are the neutral switch itself and how it is grounded inside the engine case.
Its a long time since I had my neutral switch out but I seem to remember looking in the hole and there is a ball or doohickey or something which should be visible when in neutral and which contacts the end of the neutral switch.

On the shift drum is a cam lobe that pushes on the switch at neutral. If this is not aligned properly or the screw holding it has come loose, it won't work. Sometimes the switch just wears out.
Steve

Tested continuity between the neutral light housing and the neutral switch, getting nothing when I connect the multimeter from the center of the neutral to the engine. Seems like there is no power there except the oil light lights so not sure what's goig on.

What is the proper method of testing the neutral switch itself.

msardes wrote: Tested continuity between the neutral light housing and the neutral switch, getting nothing when I connect the multimeter from the center of the neutral to the engine. Seems like there is no power there except the oil light lights so not sure what's goig on.

If there is no continuity between the bulb holder and the end of the wire at the neutral switch then it soundslike your problem is a break or bad connection between those two points.
Heres a wiring diagram from kz400.com www.kz400.com/Workshop%20manual%20bilder...anual%20P176-End.pdf
Scroll down to page 14 and follow the wires

The oil light is separarate . Same idea , a single wire from oil light to oil pressure switch and when the oil pressure comes on it breaks a circuit so the light goes off. The fact that this is working should not really relevant to the neutral switch problem.

Sorry but I dont know how to test a neutral switch. If it looks anything like the one in the picture then it should be easy to unscrew and poke about in the open end.

I have continuity between the neutral housing and the wire that connects to the neutral switch. But from what I understand in the wiring diagram the neutral and the oil and the turn signal light each have a neutral wire which gets connected to the prospective leads eithe oil or neutral or turn and then a brown wire in the cluster gets hooked up to power or the power wire in the harness. If I disconnect the neutral lead in the harness and connect it to the ground in the harness the neutral light lights up. This would make me believe either the neutral switch itself is bad or there's something else going on there.

If I disconnect the neutral lead in the harness and connect it to the ground in the harness the neutral light lights up.

Is your battery negative also grounded to the engine case ?

Battery negative grounded to the frame with the ground strap

What happens if you pull the wire connector off the center prong on the neutral switch and touch it to the engine case ? If the wiring is good then the light should come on.

? Center prong in the headlight basket or prong off the neutral switch?

The center prong on the neutral switch.
In the picture above its the little brass prong or rod pointing to the lower right side of the picture