Fuse keeps blowing - 1981 KZ750 LTD

Hey everyone,

So ... I took the bike apart the other day (tank, seat) and check the harness as suggested, with no avail. I had a look at the fuse box, which did look a little dirty. I clean it with a brass brush and some electronic cleaner solution and took the bike out for a ride for 15 mins, without any of the fuse popping. It's an encouraging result but yet again, I have been able to ride up to 25-30 mins before the fuse popped in the past.

With all of that being said, in the process of cleaning the fuse box and inspecting the rest of the wiring... I realized that one of the fuse wire was simply not connected into anything! The previous owner of the bike has simply taped it to another wire, which I thought was covering a connection. Obviously, this is less than ideal, but this has not been an issue in the past and the bike ran fine. If I am not mistaking, this also means that the 2x10A box is only holding 10A at the minute? What's the best way to proceed here?

Which colour wire was disconnected? There should be 6 wires going to the fuse box: white and white/red on bullet connectors, then a 4-way connector with blue/white, blue, brown/white and red/blue. How's your bike wired up?

EDIT: Blue/white and brown/white come from the right hand switch block and are just branches of the main brown wire that provides power to the horn, etc. This means both wires provide power from the same source so if only one is connected to the fuse box it may be connected to both fuses. Not ideal but would still be fine.

>How's your bike wired up?

It's a nightmare. To be honest, the bike should be re-wired completely but I haven't had the time to do so. The previous owner had tried to simplify the original harness... and grafted some wires on it. I have the original owner's manual and you can see some of the remnants of the original harness. At the time of purchase, I had to add turn signals, and horns, plus fix break lights so the bike would pass the safety inspection, so I grafted those onto an already pretty modified harness.

As far as I can tell it's one of the white/blue - white/brown wire that is disconnected (hard to tell with discoloration).

OK, Not jealous at all! is the remaining blue/white or brown/white wire connected to both fuses? Are the other two wires still present (blue and red/blue)?

I'll report back again on this as my bike is within my friend garage, but from memory... the white and blue is connected to a fuse, as well as the other two wires (blue and red/blue). The only one not connected is the (brown/white) wire. Obviously, as a result, the only fuse that is popping is the one connected to the blue and white wire.

OK. It would be good to know what the wire (blue or red/blue) leaving the fuse box is connected too. If only one wire is live then it will probably go to the dash lights and the headlight (via the left hand switch block). It should also go to the taillight via the ignition. Normally the headlight would be on a separate 10A fuse.
You said the bike grinds to a halt when the fuse blows. Does nothing work? Not even the starter? The ignition coils and starter should get power through the white wire connected to the 20A fuse (white -> yellow at ignition -> black (starter) and red (ignition) at the right hand switch block). If the bike stops when the 10A fuse blows then it means the coils/igniter are getting power through the same fuse as the lights. In that case I'm amazed you didn't have this problem sooner.

If the fuse is blown (filiment blown apart, black inside the glaas ect) = short somewhere. If not blown that way, fuse holders are bad. Put your finger on the fuse. You will find it too hot to touch most likely. They are too hot to touch even when working correctly, when not working correctly the fuse is hot as a soldering iron. Todays world all Kawasaki's would be recalled and an entire different design fuse system installed. In the 1970s/1980s motorcycles were not considered in recalls. All the trips I took in 300,000+ miles on these KZs, the fuse system was one of my top worries as a fuse can and will melt from the clips often.

So....
I ended up stripping the entire harness to look at all the wires individually. While this was good it truly revealed the extent to which the harness has been modified and the need for a full re-wiring.
There was a couple of damaged wires within the harness which I have taped. I also found a loose connection going into the fuse box which might have been a likely culprit.
Following one of the recommendation here, I ran the bike and wiggled some of the wire to try to identify the short, while I was never able to pop the fuse while on the stand, I did find a set of connections where wiggling the wires had an impact on the running of the engine (see attached picture). These wires seem to connect the stator to what is either the rectifier or regulator (see picture - a slighly bigger unit similar in design in under the battery box )? I haven't got to testing the electrical component individually yet. Will report today when I do.

The circled component appears to have a blue wire, so it's probably the Igniter. The wiring diagram has the wire colors:
From the 750-H2 diagram: red, yellow, black, blue to the pulsing coil; and red, black, green, black/yellow to the ignition coils.
note: the wiring diagram is showing a red wire from the igniter to the ign coils, but it might be red/yellow.

The unit under the battery box is probably the voltage regulator (reg-rec). 3 yellow wires plus black, red, brown. The 3 yellow wires go to the stator.

Thanks - that's really helpful! I took a short ride on the bike yesterday and it was running fine (no fuse were popped) - so I imagine the issue might have came from the poor connection close to the fuse box.

In the process of cleaning the wire and inspecting connection I also checked the spark plugs and realised one was damaged (plug and cap). I bought 4 new spark plugs yesterday (NGK B8ES) - but not sure how about changing the damage cap, and how to get the appropriate one. Any advice>?