Ignitors..what do they do ?

[Larry D]

The ignitor on the '81 GS450S is toast, as tested by a couple GS gurus. Which got me wondering what does an ignitor actually do ?

I have a very, very limited knowledge of electrical...stuff, I'm just trying to learn a little.

[tom203]

The ignitor on the '81 GS450S is toast, as tested by a couple GS gurus. Which got me wondering what does an ignitor actually do ?

I have a very, very limited knowledge of electrical...stuff, I'm just trying to learn a little.

It's magic! Have a read here....

http://www.thegsresources.com/_forum/showthread.php?224977-Starting-Problems-am-I-doing-this-right&p=2093152#post2093152

[Steve]

Think of them as "electronic points".

It's actually just a box of transistors that interrupt current flow through the coils, just like the points do on older bikes.

The difference is that they don't wear out and need constant adjusting like points do.

Yeah, they occasionally fail and need to be replaced, but are maintenance-free until that time.

.

[Larry D]

So.....it is like a timer that controls when the coils spark. Is that about right ?

[Steve]

So.....it is like a timer that controls when the coils spark. Is that about right ?

No, not really much of a "timer".

You know how the points actually work? Current flows through the coils and the points, which builds a magnetic field in the coils (remember the coiled wire around the nail in science class?). When the points are opened by the lobe on the end of the crank, the current stops , the magnetic field collapses and actually causes a back-flow of electricity. Since the points are open, that back-flow has nowhere to go, except to the other set of windings in the coil. Since there are a LOT more of them (the secondary windings) the voltage is much higher. THAT is where you get your spark.

The "ignitor" does pretty much the same thing, but uses a small magnet on the end of the crank instead of a lobe. There are two sensors that replace the two sets of points. When the magnet goes by the sensor, it sends a small pulse of electricity to the "ignitor". The ignitor amplifies that small pulse into a signal that is big enough to trigger some transistors that are controlling the current through the coils and stops the current flow. When the current flow stops, it's just like the points-based system, you get a spark out the secondary windings.

One of the advantages of electronic ignition is that the transistors can start the flow of electricity throught the coils quicker than points can, which will start to build that magnetic field quicker. At higher engine speeds, points might not have enough time to build enough of a magnetic field to get a proper spark, but the quicker-closing transistors will. Of course, the other advantage is the "set and forget" part, where the electronic ignition needs no further maintenance or adjustment once it is properly installed.

.

[Larry D]

Thanks for the explanation Steve. I hoping to understand all these things one day.....