78 Kz650 New battery no ignition and lights

Hi everyone, I developed a problem with my electrics seemingly out of nowhere. I had been riding around up to a hundered miles a day with very little issue other than the starter but on evening it failed to start up with the starter(not enough power to turn it over) and wouldn’t start up kicking it either(pretty uncommon as I usually kick it over). I had to bump start it in the gas station parking lot in order to get it home. I thought I might be the battery since it was left in the bike over the winter so I bought a new one and installed it but now there’s no power to the lights or ignition with the new or old battery. I just replaced all the fuses and the problem isn’t fixed, what’s my next step?

Voltmeter. Do you have voltage at the main fuse?

It doesnt look like it though I’m bad with wiring. I have the key on and the negative probe touching the negative pole of the battery, then I touched both sides of the connector for all the fuses and they read zero. Battery has 12.58V

Just checked continuity from the disconnected negative lead to all connections in the fuse box with the key on and the voltmeter showed resistance for all of them which means continuity is good, correct? Also check it to the two positive connections in the ignition switch with the same outcome.

ZoomsJr wrote: It doesnt look like it though I’m bad with wiring. I have the key on and the negative probe touching the negative pole of the battery, then I touched both sides of the connector for all the fuses and they read zero. Battery has 12.58V

To check the main fuse, you don't have to have the key on.

The black probe should be on the battery's negative terminal.
The red probe should be on the fuse which has the white wire on one end and red/white on the other.
If you don't have voltage there, then your battery is disconnected. Sometimes the battery connects to the fuses directly, but usually it connects from a post on the starter relay (aka starter solenoid).

The B2 diagram shows a dedicated red wire from the battery to a junction with the red/white wire. But after all these years someone could have altered the layout (due to damage from battery acid etc., which was common).

With they key off there wasn’t any voltage at the main (25A?) fuse so it looks like a disconnected battery is a likely culprit, thanks!

The main should be 20A.

So there was a disconnect on the positive side thanks to the previous owners wiring which I fixed. However after a brief stint on the highway my main fuse blew and melted the plastic around it leaving me stuck on the side of the road. Do I have a nasty short somewhere?

Finally got a fuse delivered and made it home 15 or more miles no problem. I was cruising at about 6-7krpm when the fuse blew for about 10-15 minutes and on the way back I didn’t pass 4500 cruising. Additionally, when cruising at 6k, the speedo showed 80mph (and was fluctuating a lot) which isn’t correct but this shouldnt be related to the current problem because it’s a fully mechanical speedo, correct?

When I replaced the fuse I had to scrape flux or something out of the out of the connector on the white wire(not red and white from the battery) before I could start it up again.

When I got home I checked voltage at the fuse at 6krpm and it was around 13.5V which seems reasonable to me. I did notice that the fuse and connectors(only the main) were hot once I was done checking it at that speed and the fuse was “cloudy” inside. Anyone have any idea what’s going on?

Your syndrome of the “cloudy” inside of the fuse indicate a heavy load of current, (Ampere), on your wiring harness with an near by shortcut to the battery negative frame/connector/two or more molten together cable somewhere in your wiring harness. The aluminum in the fuse glass housing vaporized slowly by the heat until its blowing through.
You have to check your complete wiring harness for suspicious wirings and connections.

It could be over current, but also dirty fuse holder will cause the fuse to overheat and melt, but not because of over current. First thing to do is clean clean clean, then see if the fuses get warm again. Also, look for the wire insulation turning brown from heat. That a clue of dirty connections as well.