How does an Ignition system work?

Can anybody tell me in a pretty simple way exactly how the ignition system works on a bike? How it cranks up. Preciate it. Sam

Electronic or conventional(with points?

The electronic version has magnetic pickup or Pulsing Coils that interact with a moving sensor attached to the end of the crankshaft.These connect to what Kawasaki calls the "IC Igniter" it actually gives the ignition coils their grounds, creating the energy that fires the sparkplugs.

Some of the older bikes are suffering intermittent loss of spark due to the pickup coils failing. fortunately, the pickup coils are still available from Kawasaki.

The conventional version does the spark production by having two sets(for a 4 cylinder) of spring loaded ignition points actuated by a cam on the end of the crankshaft. Anytime an electrical coil has the magnetic field collapse(like when the points open), a primary field collapse will produce a much higher level of energy in the secondary windings. Ignition coils have primary and secondary windings.

For the most part,todays motorcycle have electronic ignitions as it does not have parts to wear out like the points system does. And is much easier to adjust for tuning.

Mfolks pretty much covered the overview of the topic relative to KZ's.

Kz's only use what is known as Kettering ignitions. They are also called flyback ignitions. They are not CDI as they are sometimes incorrectly referred to.

Kettering originally used points, and you can google Kettering ignition to get the theory of how it works.

Later, transistors were used instead of points to create a "tansistorized Kettering" ignition. That is the type of electronic ignition found on later KZ's. Of those, there are two types: mechanical advance, and electronic advance. The mechanical advance type is far more common.

To tell you exactly how it works, would take a book, or even multiple books to explain all of the electrical theory behind it.

But for the basics, a search of google for Kettering ignition will probably turn up a bunch of decent sites.

Nice! I hoped my explanation will satisfy his question, I didn't want to get in to theory of operation(when that happens, peoples eyes tend to glaze over and you've lost them).

MFolks wrote: Nice! I hoped my explanation will satisfy his question, I didn't want to get in to theory of operation(when that happens, peoples eyes tend to glaze over and you've lost them).

Like this ... :blink:


I know the feeling.

Man alive, I was fighting the glaze. So my '84 probably works conventional? And then what does CDI stand for? I'm gonna google the kettering ignitions. Thanks for the insight fellows.

My fault. I didn't follow up like I wanted to. So after your description Mfolks, is this what goes on in a conventional setup... we turn the key and press the starter switch, this triggers the crankshaft with the cam which opens the the spring loaded ignition points, makes the magnetic field collapse causing a huge amount of electrical energy which flows through the secondary windings and fires the plugs??? That's what I got from it. I hope I'm not too far off base. Thanks for the wisdom again

Yep, that pretty much describes what happens when the start button is pushed and the ignition system is working(thet are two seperate systems). At least on the Kawasaki bikes.

The stock Kettering (points) type ignition is a classic flyback converter which steps up a relatively low voltage (12V) to a high voltage (about 40kV) using a transformer with a high secondary/primary turns ration. The piece called a "coil" is actually a transformer.

The way it works: points close and current flows in the primery which stores energy in the core of the transformer. When the points open, the rapidly decreasing primary current forces a volatage of about 300V across the points which also forces it across the primary. That voltage is steeped up by the transformer turns ratio to a maximum of about 40kV at the secondary (spark plug) side. The actual secondary voltage is limited by the spark plug: the voltage builds up until it's high enough to jump the air gap with the spark and that clamps the voltage at whatever that voltage is.