does the primary always make high voltage kickback?

what are the voltages if it does make kickback spikes?

 

hi pager,
Lenz's Law.
Look thru this link.
E
https://www.google.com/search?q=lenz's+law+equation&ie=utf-8&oe=utf-8&client=firefox-b

 

does the primary always make high voltage kickback?

Yes

what are the voltages if it does make kickback spikes?

Depends on the coils winding ratio. The old 12V round coils had somewhere around 200V to 400V depending on the coil.

This is a good thing to read/follow when doing this with a 555 - https://www.rmcybernetics.com/science/diy-devices/diy-ignition-coil-driver The whole site has good ideas for what you're doing - https://www.rmcybernetics.com/science/diy-projects

 

The primary kickback spike, caused by the energy stored in the coil inductance, is what generates the secondary high voltage spark.

 

The fundamental relationship between the spike voltage and the other terms is given by E=L di/dt, which means that the faster the current changes the greater the spike voltage will be. And it implies that the greater the current is initially the greater the spike voltage will be. Of course it may be difficult to know just exactly how fast the current is changing, because in a real situation with actual contacts opening there is often an arc, which is conductive, and thus acts as a resistor that affects the rate of current change.
So the result is that it takes more than just a 555 timer IC to produce some high voltage from an automotive ignition coil.