"Normally" an alternator failing will not stop a motor in its tracks. There is residual voltage in the battery that should keep the car running for many miles and only start to show signs of dying when you're slow or hit the brakes to use more juice from the battery with brake lights.

My guess is that something in the electrical system crapped out and killed not only the alternator, but the battery as well.

I would check fuses, wiring etc before condemning the alternator.

If it IS the alternator, this will not be an easy fix on a M3W. As the motor will need to be pulled and the compensator will need to be removed to get to the rotor and stator. Whether a Harley or a M3W, this will take lots of time to fix.

Again though, my guess is something else is at fault for it to shut down the motor only seconds after you lost voltage output.

When you turn on the ignition, what voltage does your meter show? It should show something for voltage, not just zero.

Good luck with sorting out your issue.

Dan