New Kz650 owner...need some help

Hello i am excited to be the new owner of a 1979 kz650. Everything went perfect until this morning and now im in need of some advice. I bought the bike two weeks ago and put over 300 worry free miles on it so far, always starts right up even in the mornings. This morning after not riding it for a few days i turned it on (started right up) and left it warming up for a few minutes. After i went inside i heard it turn off (normal in this bike since the idle is a tidy bit low until is fully warmed up). When i went back outside i noticed the lights had stayed on and now the battery seemed to be dead. I jumped the battery and it turned on again so i decided to go around the block real quick. When i got to the corner it shut off and didnt even turn over. Now a few hours later i tried and it starts right away but after a while it turns off and if you re try to start it it turns pver but wont start. I was thinking maybe the coil or coils went bad but id appreciate some more knowledgeable input. Thank you and sorry for the long post!

Start at the battery and work your way back through the charging system.

The battery could have died - they do that sometimes.
The regulator or rectifier could have fried.
You could have lost the charging coils in the alternator.

Some of the 650s use a single phase charging coil in the alternator, and when it goes, the bike will not charge. If you find your alternator is the culprit, there is an "upgrade" which allows you to use the 3-phase charging system from one of the "about that time period" bikes (750 comes to mind) to replace yours. Much more power available and more reliable.

Don't panic. Start with the battery and check everything in the charging system before you jump to conclusions.

I would check the battery. A digital multimeter is handy & a good battery charger. I have a VC97 & Ctek US 0.8.

You've probably already figured this out, but when the ignition switch key is in the ON position, the lights come on & stay on. So even if the engine stops, the lights still have power & will drain the battery. Also, it's kind of a bad idea to leave the bike unattended while running... you never know what could happen. One possibility is blued pipes from lack of air flow if the idle creeps up too high.

forgot to mention the battery is brand new

I don't think its a battery problem. Fuel delivery because it runs a short while after starting. Tank insides rusty? Been a while since the fuel filter was looked at? Disconnect the fuel line to the carbs and see if the fuel flows with the selector valve on "prime" if you have a vacuum petcock. "On" if you have a normal petcock. If your fuel flows healthy perhaps the carbs need a cleaning. If it all checks out, go to plan "B".
Get a volt meter and after starting the bike up measure the volts at the battery. Rev it up and see if the volts increase to what ever the regulator is set to. If the volts do not increase, there's your problem.
Happy Hunting.

santiagokz650 wrote: forgot to mention the battery is brand new

The first thing I would do is check the battery. It's one of the easiest things to do, so why not?
What type of battery is it & did you follow the proper service procedure prior to installation?
If you don't have a good battery charger, get one.