Could someone please explain to me how the coil packs on an NC30/35 work? Not as in the part where they convert 12V at a small current into thousands of volts at a minute current to create the spark, but specifically how each coil knows when to fire? The wiring diagram shows that both coils are on the same 10A feed from the battery as the ignition box, and then each one also has a second connection back to the ignition. So, this is where I get confused. To me, it appears that each coil only has one wire on it issuing an instruction to fire, and the other is providing the power to energise it. So how does the coil pack know which of the two HT leads should be energised?

Also, there's reference to the coils being grounded via the frame, hence having metal mountings, yet the only earth in the circuit according to the diagram is via the spark plug. Is this just to simplify the diagram?

It's a wasted spark system.

Front fire at the same time, so do the rear.

As above.

They fire both leads at the same time, wasted spark.

You can do this with most I4 bikes and 360 degree V4s due to the fact that two pistons are always at top dead centre together. (even though only one has fuel mix in it)

The NC21 / NC24 which fire 180 degrees, along with the VFR750/800s have 4 coil packs as none of their pistons are ever at the same place of the stroke together so can't share a spark.

Ah, I did wonder if that was the case, but wasn't sure if there might be issues with firing both at the same time. Clearly not! Ta.