Pull the dizzy out and grasp the top of the spindle with needle nose pliers and try turning it side to side. I imagine there is some play but if really loose maybe it's f'd up.
One last thing is the crank bolt tight?
That and/or the cam bolt. He says they are tight.
A rod bearing could be the noise. If you catch it in time, you could just polish the crank with some super fine emery cloth and put a new bearing in. You can do that without pulling the motor. If you didn't catch it in time............!