help please

On my Z1 and KZ900, a weak battery results in weak spark which causes missing.

As the battery increasingly deteriorates while riding, the spark eventually gets weak enough to prevent running. This has happened while touring, where a new battery resolved the issue.

Neither bike will start or run absent sufficient power to the coils.
Neither bike will start or run with a dead battery.
Neither bike will start or run without a battery.

In my experience, a failing battery is destined to cause headaches sooner or later, and I prefer installing a new battery the sooner the better. Same with the car-van-truck.

A load test is usually beneficial to battery diagnosis, and available free at the local auto supply store such as Auto-Zone.

For an accurate load test, it's best to add distilled water as needed and charge the battery overnight before having it load-tested.

Good Fortune!