Harmonic Vibration 3500-4000 RPM

Neutral: I've had it give me bad vibes in neutral before, but I just took it around the block and revved it in neutral in my driveway, and there was no thrumming vibration. I'm going to take it out for spin this afternoon.

It's a 318.

I was looking at the pulleys, and I saw that the crank pulley had a slight wobble.

I'm wondering if there's something going on with the ignition.