TOPIC:

Here's a simple way of looking at how an ignition coil simultaneously fires two spark plugs.

When the ignition coil is receiving battery+ voltage (normally when the ignition key switch is turned ON), and while the coil's primary wiring is grounded through closed points, the coil's primary winding has current through it (from the battery+ post > coil primary terminal > through the primary winding > the coil's other primary terminal > closed points > ground. Whereby the coil has battery voltage in it's primary winding.

The opening of the points interrupts the primary wiring's path to ground, which is the event that causes the coil to magically and simultaneously "fire" both spark plugs.

The "firing" takes place throughout the secondary loop, which is shown below:





An unwanted break in the secondary loop will prevent the high tension voltage from circulating through the secondary loop, which prevents either spark plug from firing.
For example, removing one spark plug cap prevents firing of either plug within the secondary loop (i.e., neither plug fires, meaning neither plug has any spark).



When only one of the spark plug pair is firing, the non-firing plug is still allowing passage of high tension voltage (eg., through a carbon-encrusted plug gap.)



Good Fortune!

Hey Patton....

That is a very detailed and well diagram explanation of how it all works. Thanks a bunch.
I learned a lot from this diagram.

The bike purring like kitty. I'm going to leave it as is.

Thanks.