Villiers ignition problem

[StephenRT]

I attempted to start my barge pusher this morning. Found there was no spark so tried points cleaning and adjustment but to no avail.

Decided to check the coil and found that the HT winding was open circuit.

Removed the flywheel and backplate to find this.

It looks like there has been an explosion within the windings, any ideas?

Thanks

Steve

[phil]

Small break in secondary winding, sparking across, eventually grows wide enough that spark won't jump gap. While this is happening, the location is close enough to the surface of the secondary winding that the constant sparking burns a hole through the paper covering. That would be my guess.