1977 KZ750 twin electrical issues

I’ve got a 1977 KZ750 twin. It will start with the kickstarter, it will sometimes start with the starter, but sometimes won’t. When I turn the key one the running lights come on dimly and flicker while the starter is rolling over, even with all lights turned off. Sometimes after it starts it will just shut off. Any ideas? Thanks for the help

Your battery have no sufficient performance/power.
Check the battery acid level is low and if necessary fill up with distilled water.

It rolls over just fine. It’s a new, sealed battery.

Could be a loose or broken wire. I'd start with both ends of the battery cables, then with all the ignition wiring.