Headlight power wire heats up -- ground issue?

I have a 1988 KZ 1000 P motorcycle. Right now my headlight is not turning on but I isolated and figured out the location of the problem. It is an in-line fuse on a wire. I placed a screw in the fuse holder and the headlight went on. But the wire in that specific area of the fuse holder started heating up with immense heat. I am wondering if there is a bad ground. What do you guys think? Before for some reason I disconnected all of the grounds underneath the seat I found three grounds to reconnect when I was putting things back together. For some reason I thought I had to disconnect these specific grounds in order to remove the battery but I did not. I wasn't able to finish the project that day so time went by and I when I went to reconnect everything there was only three grounds but it is my firm belief there was a fourth. You can see in the picture here a missing space of where I believe the fourth ground was. What do you guys think based on the picture? I think I know where the fourth ground wire is supposed to come from but I'm not sure I'm not very patient when it comes to reading electrical diagrams so I'm looking for somebody or someone's opinion on where they think the fourth ground comes from. I believe this could be the issue of why this wire is heating up in The in-line fuse area. In the picture I am holding the in-line fuse and in the second picture I am pointing to where I believe the fourth ground is supposed to go in the third picture I am holding a wire that I think it's supposed to be the ground but I do not know and I am looking for affirmation and confirmation on what to do.

I'd say that the fuse is a symptom, not the problem. An overheated wire suggests very high resistance. This is frequently caused by dirty, corroded or loose connections in the circuit. Badly frayed or broken wires can also be the cause. A completely disconnected ground wire will not overheat the circuit since no electricity can flow.
The pic shows several crimp connectors. If not properly done, they can introduce unwanted resistance. My guess is that you need to spend some time with your multi-meter carefully testing each section of the headlight circuit. Each time you connect the meter, wiggle the wire a bit in case there is internal breakage that cannot be seen. Yes, this can get a bit tedious.

High/low beam connections or contacts can be dirty or stuck.
Steve

my mistake. I now see that the headlight is not coming on. doh.

On the actual handlebar switch itself?

For Texas kz,

I'm going to try and replace the inline fuse and a couple of poor crimp connections, but the funny thing is that the high beam indicator actually doesn't work now

Hawk111 wrote: On the actual handlebar switch itself?

Yes
Steve

Your battery ground point looks badly corroded as does the wiring going in and out, also ground is black/yellow on these.

If the 1000P has a 7 way fusebox then you should have a seperate fuse for the headlights and this should be powering the circuit. (The 7 way fusebox can develop internal faults )

The inline fuse maybe from an accesories terminal, but it is not right also headlight wiring is thick guage to cope with a high current draw.

Dodgy block connector(s), headlight/beam switch, fusebox or ignition switch plus bad grounding would be the usual suspects. I add an extra ground at the front and back of a bike always.

If the wires and crimp connectors look bad you can be sure the meter will measure them as high resistance.

Messy wiring like that is at best a breakdown and worse an accident waiting to happen.

Headlights are the largest power user on a motorcycle, and they're quite voltage sensitive; a couple of missing volts will degrade your lighting a lot.
The current will typically run through a fuse, the ignition switch, the headlight on/off switch, and the high/low switch. The wiring is usually barely sufficient when the bike is new.
After servicing many old vehicles, including bikes, I've found that those old switches lose between 0.1 and 0.5V each.
The solution is easy; headlight relays.
Just use the existing lines to power the relay coils instead of the headlight. Run a new wire, with a new good quality fuse holder, to the relays.one for highbeam, one for low.
Make sure the ground wire is robust and clean too, or better yet run a new one to the engine or battery negative.
Don't use crimp connectors, solder everything. It takes a little more time, but as I told my Portuguese neighbor while I was rewiring his 40 year old tractor; crimps, 1 or 2 years. Solder, 100 years.

You'll see a huge difference in light output with a relay. All cars have them now, and bikes really should.

I used to do a lot of riding at night, on unlit country roads. A 100 / 55 W headlight bulb was the difference between seeing and not seeing. Without a relay, the connectors would start to smoke after a minute.

Ive been busy with my electrics for a while now and one thing I noticed is that the 3 wires going to the headlight (yellow/red, black/red and black/yellow. I think ) are a heavier gauge than the rest of the wiring. If youre going to replace them make sure theyre the right gauge.
Also,I found,on the fusebox and on the ignition switch I had wires that,at first,looked well fixed and healthy but on closer inspection were worn out and holding on by a few fuzzy green strands. Dont take anything for granted,peel everything back so you can get a good look and make sure its all hunky dory
Finally, Im interested in what Mark in Portugal says as Ive read recently that soldering is not as reliable as you would think.Apparently solders can break apart over time from vibration amongst other things. Im not an electrician so I cant say one way or t'other. I would have thought that soldering,especially splices, would be a good reliable method but when I stripped my loom I found that all the OEM splices were crimped and wrapped up in insulation tape. This was from the factory and seemed a bit of a cheap fix.
Good luck with it

There can be issues when soldering to lugs that are screwed down to vibrating things [like engines]. The stiff wire can break at the end of the lug.
The solution is not to let the solder wick up the wire on those applications. So what you do is put the stripped clean wire in an uninsulated crimp connector, crimp it, and then heat the lug end until the center of the connector is hot enough for the solder to flow, but avoiding letting the end get that hot. Just a dab of solder to the middle is all you need. Sometimes I hold the tail with vise grips to wick heat away. With big connectors for truck / boat battery terminals, I use a propane torch.
I also add a piece of heat shrink tube to seal the wire from corrosion.
I've been soldering all low voltage connectors on cars, trucks, tractors, bikes, and boats for 40 years, and only 1 broke [about 30 years ago].
Crimp connections are used by the factory because it's cheap; and works fine when everything's new, and for the first 10 years or so. When the wires start to corrode, even a little bit, crimped connectors will have extra resistance. The resulting heat will add to the problem, strands will become brittle and break, and soon you get failure.
If the coper is black or green from corrosion, you'll have to clean it before soldering or it won't wet. I use a sharp blade, but some folks use acid.

I've had trouble with the wide blade connectors on the headlights; they tend to overheat and melt the plastic when used on the 100w bulbs. I change them for new and add some white grease to the connections to help dissipate the heat and keep the oxygen off of it all.

Thanks Mark. Good to know.