Headlight does not come on

On google:
images for 2005 Yamaha TT-R 125 L light relay

It could be the link from the starter button to the ignition coil. If you can check this for a current it should give an indication of the problem.

Sounds more like the battery may be dead... take the battery to O'Reilly's or Autozone and check the CCA (Cold Cranking Amps).. amperage is what starts your bike.. not voltage.. then see what happens...Next, its time to trace voltage.. make sure you are getting voltage from the battery to the solenoid.. then from the solenoid to the starter,,

Check the fuses

you may have cut or broke a wire while repairing your harness and it may be the main wire[orange] or white to the kill switch. Fran [mechanic]

try wire brushing the connections

If there is any exposed bare wires near metal - tape them up!
Finding a short must be done methodically along each part of the system 1 bit after another
Bikes of this age tend to suffer from broken or worn bare wires in the loom around the headstock as its the only area where the loom is constantly moved
Ride Safe
Bike-Doc

sounds like you have a bad relay switch. if you have an ohm meter or a multi meter check the relays that are past the fuses

98 honda shadow ace wont start electric switch is sticking and the headlight doesnt come on when key is turned on

Hi and welcome to FixYa,

Depending on the version, normally there would be two (2) relays for most Kawasakis that control the headlight(s). Often the hi-lo relays (with white connectors) would be behind the gauges. Again depending on the model, some would not have a headlight on/park/off but only hi-lo as the headlights automatically switch on when the engine is running.

Just a start, do postback how things turned up or should you need additional information. Good luck and Thank you for using FixYa.