Pulsing coil ignition alternatives

If you have spark advance, I would guess there is/was a vacuum line to the "brain" (ECU)? That controls, and is one of the big reasons for, the spark advance.

Like many small magneto-type engines, a magnet in the rotor acts as the crank position sensor. That is probably also in this system.

Magnetic pickups have replaced mechanical points for a long time. They can be used to sense position or RPM as well. Most magnetic pickups have a magnetized core material. As something ferrous approaches the core, the flux in the core changes. It is the change in flux that generates the voltage. Outputs can be anywhere from millivolts to volts. The speed of the passing metal and how close the metal is has alot to do with the output voltage. The output waveshape depends on the shape of the material being sensed, for example a square toothed gear would generate pulses at its edges, different from the pulse generated at the flat of the tooth. Part of the waveform is generated as the tooth enters the flux and part is generated as the tooth exits the flux. Usually a magnetic pickup is followed by amplification, filtering and something to clip it into a clean square wave. The short answere is that the sensor could be outputting almost anything. As long as you can measure continuity and the core is still magnetized, it is probably still good.

I can't recall if there's vacuum to the igniter box, I don't think there is, only electric wires. That's not to say that one of those wires isn't the output of a pressure sensor somewhere.

Yeah, my cores are still magnetized and I have continuity, but my resistance across them is about 500 ohms and my manual says it needs to be 360-440ohms. So I'm looking to alternatives as the pulsing coil cores aren't made anymore for this bike. I'm wondering if as the resistance increases (due to heat and age?) if the voltage drops, can I maybe bring the rotor closer (so it passes closer) and increase voltage again to usable levels.

Also I didn't realize the shape of the rotor mattered so much, I guess I won't attempt to modify it or anything.

Do you know of a resource I can look at for more information on how it exactly works? I think I know most of the theory behind it but not when it's in this particular configuration. I don't recall any of the formulas either, getting the exact relation between speed, proximity and output voltage would be great.

Thanks so much.

I thought I replied to this... guess I'll try again. Forgive me if two posts show up.

I have continuity across my cores, the problem is the resistance across them is 500ohms and according to the manual it should be 360-440ohms. Heat and age ruins them I guess. My rotor is most definately nonferrous, so this confuses me. Is there anywhere you can refer me to more about this specific setup and the theory behind it? A formula to relate voltage out to the rotor speed and proximity would be great, maybe I can decrease the proximity and up the voltage to compensate for my increased resistance.

I'm familiar with the basic electromagnetic field theorys, for instance the laws that govern how electric motors and generators work, but I am still missing something to understand how this works.

As for the ignitor box, it does not receive any vacuum line, but it may receive electric from a vacuum sensor, I'm unsure.

The same laws that govern a generator apply - magnetic field cutting thru a conductor

It might be a centrifugal advance or done in software if the brain box has a computer.

What problem are you having, no ignition, misfire? Five hundred ohms is not very far off from where you should be. Your ohm meter might be out of calibration too. I would expect shorted turns or an open coil to be a more common failure than the resistance to go up. The only reason resistance would go up is if you had corroded connections or perhaps the winding overheated somehow. There should be some signs of discoloration or melting somewhere if heat was an issue. But ... you still don't have the information as to what the output should be or even if the brain box is functioning correctly. If I were you, I'd use google or call a Kawasaki shop to get the information you need. If you have access to an oscilloscope, it will show you alot more than a multimeter can. An Oscope will show peak output volts and the waveshape, where most general purpose multimeters only measure 60 cycle sine waves. I would guess that the pickups would probably put out about 1 volt peak at

1000 RPM , 2 volts peak at 2000 rpm, 3v at 3000 and so on. Outputs in the millivolt range would tend to pickup ignition noise and require much more amplification, but this is just a guess. For more output from the pickups here are some options - Closer gap to the rotor More turns of wire on the pickup coils Stronger magnets Change the rotor material to something like nickel (not likely).

I would refer the snowmobile guy to:

It comes with a MAP sensor and you just feed it rpm input and you're set. If he doesn't want the nice enclosure it's $15 for the circuitboard itself.

I could go this route but still have to fab up a different crank sensor, I'm hoping for an easier way out. It is a cool thing though and the molex connector looks exactly like the input on my 'brain', maybe I'll play with it as well.

Yes, I was told that lower ohms means grounded and higher means open, but didn't fully understand the reference.

My particular problem with my bike is it runs very rough (sometimes) and will die randomly. The symptoms sound exactly like the problem of needing a new pulsing coil and mine does have ohms out of range. I have not watched to see if I'm getting voltage out or not. I guess I should hook a voltmeter inline and see if when I get the bogging there is some change, like you said though and oscilloscope would be best.

I can't picture a coil of wire being intermittant other than a loose connection or cracked pole pieces. If it has weak output, it might be right on the edge of working though. While the bike is running good, would be a good time to measure the output so you know what the replacement needs to put out. Remember that the output voltage will vary with RPM.