kz550 dead, 12v down on ignition and light line.

Greetings from UK.
Need your expert advice please.
Bike was running and just had MOT, Passed fine.
On the way home in a van (no tax or insurance) forgot to put it into gear and slipped from harness.
The Key module which is placed on the left side of the bike(custom cafe racer purchased cheap) got hit and i suspect might of grounded the back solder joints.
The bike now wont start, no lights nada...
Measured the volts into the 5 pot key module (white cable) and got 12v, when i flip the key over to run it drops to 2v, which is also present on the yellow (ignition) and brown (lights) line. I cant see any squashing of cables and have checked the fuses. I removed the key module and bridged at the connector and same result.
Im no electrical guru and cant see how its dropping voltage.
Any help on this would be amazing, as im baffled..
attached couple of pictures
regards martin

You may have a short somewhere after the ignition (on yellow or brown or...). I would unplug the ignition and just short the white and yellow, then see if it starts. If not, short the white and brown and see if the lights work. I expect one of the circuits will be fine. What are the blue and red wires? The taillight circuit?

Check the fuses and battery voltage.

My guess is you have high resistance on the yellow wire. The wire could be crimped, pulled, or a faulty connector. This would in turn break many of the strands but...not all of them. Just enough to give you 12 volts with no load.
When you load the circuit...the voltage drops to 2 volts because of the restriction in the yellow wire

Either that or a connector got pulled out of a plug.

Put your positive meter lead on the yellow wire at the key switch. Negative meter lead on the battery negative terminal not the negative cable.
Turn the key on so the 2 volts shows up on the meter that you were getting earlier. ..Probe along the yellow wire away from the key switch till you find 12 volts. When you find 12 volts that will be where your issue is.

I'm not a fan of piercing cables with a needle due to future corrosion but you may not have a choice. You should seal it with this if you do pierce the wire.

www.amazon.co.uk/Insulating-Tape-Liquid-...&sr=1-1-catcorr&th=1

F64 wrote: My guess is you have high resistance on the yellow wire. The wire could be crimped, pulled, or a faulty connector. This would in turn break many of the strands but...not all of them. Just enough to give you 12 volts with no load.
When you load the circuit...the voltage drops to 2 volts because of the restriction in the yellow wire

Good thinking! But wouldn't the damage have to be on the white wire (battery +ve)? If the yellow wire had increased resistance you would still get 12V at the ignition if the white wire was intact. The voltage would just drop further down the line.

yep.. it's the white wire instead of the yellow.

BIG CAPS THANKS!!..
Problem found and resolved
The main fuse had gone, but not visable, only with a meter and also intermitant, so wire was loose inside... Also found plastic slightly melted from heat, guessing voltage drop as not completly disconnected. learnt not to assume and always check with a meter.

Thanks again guys.

Good to hear you got it sorted. Hope there was no other damage to the bike.