1977 KZ750 Died at a traffic light, no electrical at all!

So, I hadn't ridden the bike all Winter. Last week, I got some fresh gas, checked the oil and kick started the bike. Started in 2 tries. (Bike starter never worked for years).

I took a few short rides around the neighborhood, for 3 days, just to get the juices flowing and everything was fine. The bike sounded like it needed a carb cleaning and tune up. However, everything was great.

Friday night, I take the bike on a longer trip, about 5-7 miles and when I finally hit a traffic light.....everything just died. I rolled up to the light in neutral, and all electrical went off. So did the engine. Nothing.

No turn signals, no dash lights, no head light, no neutral light, no horn...NOTHING.

Wouldn't start with my kickstarter either. Had the battery checked the next day, its fine.

What could it be? Any ideas? need some help.

Fuses?
Steve

I know that in the past I lost all power and it ended up being the power line to the key switch and its poor solder connection.

Ditto gd4now

Would also check the negative battery cable to where it attaches to the frame to make sure it's not rusted & or corroded, so you're getting a good ground. ,,Pete

So I did a visual check of the fuse box....all good, no blown fuses
Checked the negative battery cable.... clean and good

Can’t check the key switch....but would that really cut power when I reached the traffic light.?
I mean, the bike was running well for 5 miles and everything was going fine. Then all of a sudden at the light it just died.

Still searching:-((

GR77KZ750 wrote: So I did a visual check of the fuse box....all good, no blown fuses
Checked the negative battery cable.... clean and good

Can’t check the key switch....but would that really cut power when I reached the traffic light.?
I mean, the bike was running well for 5 miles and everything was going fine. Then all of a sudden at the light it just died.

Still searching:-((

Could do, If the connection was poor it could only take a small jolt to break it completely. Mine was fine, running perfectly and the main white power from the loom to the switch parted ways on a perfectly smooth road. Nothing untoward, no pot holes, sharp breaking just riding along then nothing.

you only need to take the back of the idiot lights off to check it, well on a 650 you do anyway.

You could check the ignition switch by back-probing its connector inside the headlight bucket >> the white wire is usually the main power wire to the ignition switch. Also as 650ed has often mentioned, a fuse can look good visually, but the filament can be broken at an end cap, so you can't see the problem. So either test the fuse with a meter or replace it. simple thing would be to check for voltage on each end of the fuse while it's installed in the fuse box.


....

On mine kz650 sr 81, the power cable was jointed before they entered front light around wheel steering. I think the jointed orginal.

So I have had the same problem with the jointed.

Use the elimitate metod with a multimeter and see where you loose power was my procedure to find the problem.

Wiring diagram and multimeter is what you need.