Help FZR250 Temp gauge rises when lights are turned on?

I haven't checked the main earths yet, wasn't sure what to look for but now I know, thanks @my67xr @GreyImport.
I'll check them tomorrow morning after getting some dielectric grease, need some for the reg/rec I installed the other day too.

 

@my67xr where did you test the resistance through? Did you disconnect the earth wire off the frame and measure from the wire back to anywhere else on the frame or..?

 

If I go direct to the frame and there's no improvement would it be safe to say the main earth wire is to blame or at least needs some attention? I'll try that first before checking the main earth wire just for reference. Cheers

 

@my67xr awesome I'll post tomorrow morning my findings. Cheers

 

Hey guys so I've wired in an extra earth wire from both headlight plugs to the frame and tested the gauge with lights on etc and she's not jumping as we all expected. I tested the resistance from the earth behind the temp gauge to the battery negative and it read 0.5 with the multi meter set to 200. I also removed and cleaned up the main earth wire from the battery negative to the engine and applied dielectric grease. Tested again and made no difference. Not sure exactly how many ohms 0.5 on the 200 scale reads but I'm sure you guys will.
I've applied dielectric grease to the reg/rec and all the wiring contacts I've been playing with to the frame etc.
So now I'm just letting her cool down and will flush the coolant system with 1/3 cleaning vinegar and 2/3 distilled water. I'll flush a couple times doing a heat cycle between each, I'll then flush it one last time with only distilled water before draining it and filling with coolant.
I'll then take her for a ride and report back how the temp goes.
The wiring is semi-temporary as I'm waiting on wire crimp fittings and a new tip for my soldering iron.

 

Ah okay I was under the impression that vinegar would do harm to any aluminium if left for a period of time. I’ve done two flushes so far, the first flush drained was very rusty and am just waiting for it to cool down before I drain it again and flush it with only distilled water.
Yup the thermostat housing and thermostat in there atm is all complete.
Ah that’s good news about the resistance - clearly not that clued up about reading ohms.
Here’s a photo of the first flush fluid once drained, I’ll upload the next later tonight.
The temp doesn’t get higher than half way now btw even with the fan off so looking positive.

 

First two photos are the new earth wires.

 

No idea too be honest, what I imagine is there’s a poor earth somewhere in the loom and when I turn the lights on it’s drawing more current via the gauge earth and or sensor wire causing the gauge to read higher - or better yet WAS and no longer is with many thanks to 2fiftycc and everyone who’s been helping me along the way!
Since running extra earth wires from the headlights to the frame there’s no longer any issue with the gauge and as I type the final flush is cooling before I drain it and fill with coolant. Here’s a photo of the second flush fluid.


The green container doesn’t help with imagery but it’s a lot cleaner than the first. The final is only distilled water which I’ll drain into a clear or white container.

 

From the water pump up and the radiator cap down?
I take it the coolant will neutralise any unwanted ‘stuff’ in the tap water?

 

Yeah I cleaned it up so it was shinning, same with the bolt and where it meets the frame and also used dielectric grease. I know it's rough atm but with level 3 here in NZ it's a massive pain to get the parts I need to do it properly.