FJRiders.com

Ok, ok you forced my hand. I'm posting about bench testing ignition coils from a 1979 KZ1300 not an FJR. But both platforms use a 'wasted spark' ignition system so commonality exists.

Installed new YellowSquare ignition coils. Bike still didn't run good.
Ground plugs to valve cover, crank engine, hmm, maybe I kinda sorta spark but not like WOW, look at THAT!

Time to bench test the coils.

Search Google. Find this. Ez pz.

Batt + to coil +
Coil neg to switch to batt neg
Ground spark plug(s) shank to Batt neg
Connect both spark plugs shank together (wasted spark systems require this connection)
Hi tension leads to sparkplug caps

Close then Open switch, primary field collapses, induces hi voltage in secondary, discharges through plug.

But. It doesn't work. No spark.

WTFO? Not likely all coils are bad. Must be test set up.

Check all wires for continuity
Check plug resistance
Check switch
Everything checked out SAT

Got to thinking. Auto ignition coils use a condenser to prevent premature point pitting - due to high voltage induced into points. The condenser blocks that voltage.

Installed a condenser and voila, spark.



Question 1
What I don't know is why adding the condenser enables plugs to spark. Could it be the switch, as it opens the primary to induce field collapse and 2ndry discharge is discharging though the switch contact?


Don't find answer about condenser. But in doing research, find *one* reference that weak / no spark can be result of coil primary over saturation. The KZ has 8000 rpm redline. 8000/60 means a spark event (build up primary EMF, open circuit collapse field, induce secondary, discharge spark) has to occur every 7.5 milliSeconds. That's FAST!

A typical spark duration is ~1.3 milliSeconds. Sooo, the primary has to establish full field in 7.5 mS minus the 1.2mS for spark duration which equals 6.3 mS.

Obviously, I can't toggle the switch that breaks the primary negative side faster than about once per second. Meaning the primary flux is over saturated.

Question 2
What I don't know (a LOT ) is how severe the high voltage degradation is given an over saturated primary?

Research revealed this beauty, a Hall effect pulse width modulator that can test devices requiring a pulse - stepper motors, fuel injectors AND ignition coils. It's coming from <gasp> China on a slow boat.
https://www.amazon.com/dp/B0CZ84R1JC?ps ... ct_details

[youtube]https://www.youtube.com/watch?v=ONyoQfe6ngA[/youtube]

Hoping someone a whole lot 'fart smeller' than me can chime in with facts, ideas, thoughts.

I know, it's a technical rant. But it's real to me!

For the complete diatribe...
https://candybuttorg.ipage.com/cba/node/1430

dcarver,

From what I know of inductors (coils), over-saturation should not have much (if any) effect on spark.
The condenser (capacitor) just protects the contact points from arcing damage, whether inside an old car or your manual switch.
Electrical potential is measured in Volts.
Power is measured in Watts.
Resistance is measured in Ohms.
Inductance is best measured in Henries, for any coil. A less certain coil measurement can be done in Ohms, but that can be deceiving.
(Each standard is named in honor of the guy known for research on that aspect of electrical theory.)

All that to say this: measure a new or known good coil with a Henry meter. They are rare, but a good electronics shop might have one.
The Henries values of the primary coil and the secondary coil will be very different, but should match the measurements of a known good unit.
Coils generally fail by internal shorting, changing the Henries values you measure, until the coil goes open-circuit internally
Partially shorted primaries will change the spark voltage, but may lessen the duration.
Partially shorted secondaries will reduce the spark voltage.
The bench test rig you have is a quick-and-dirty Go/Nogo level of testing. It really won't tell you much about the internal condition of the coils, unless they are already dying.
FWIW, I would look into the coil-over-plug mod, if I even suspected that I had bad coils in my bike. You only send low-Voltage pulses to each plug, with the coil-over-plug mod. High-tension wiring is eliminated.
HTH.

Don't know anything.... but assuming the KZ does not have a condenser or points ignition, like an old Honda I just got.
Question, you've got the wires directly to the plugs...... are there not spark plug adapters, and don't they have a resistance of like 5k ohms?? I don't know if that is an issue or not.......

My concern is lack of current limiting from battery through the primary side of the ignition coil.

Re: condenser, I don't know. The coil works to continue current flowing when the switch is broken but ultimately dumps it's field in the secondary. Maybe the condenser forces this to occur quicker?

raYzerman wrote: ↑Tue Jun 11, 2024 9:12 pm Don't know anything.... but assuming the KZ does not have a condenser or points ignition, like an old Honda I just got.
Question, you've got the wires directly to the plugs...... are there not spark plug adapters, and don't they have a resistance of like 5k ohms?? I don't know if that is an issue or not.......

I don't know either, but good observation. I do have some 5k caps around.. worth a try! The KZ runs electronically, not mechanically. 3 pick up coils to provide pulse, an 'ignitor' that's 3 Darlington transistors, then 3 coils.

N4HHE wrote: ↑Tue Jun 11, 2024 11:54 pm My concern is lack of current limiting from battery through the primary side of the ignition coil.

Re: condenser, I don't know. The coil works to continue current flowing when the switch is broken but ultimately dumps it's field in the secondary. Maybe the condenser forces this to occur quicker?

Overheating the coil can happen if powered on continuously. I saw a video to prove it . On the bench, cycle the switch on and off as fast as my fingers can.

Hopefully I’m doing the math correctly here.. If coil primary is charging (putting winding under stress) every 6.2 milliseconds, then discharging (winding not stressed) for 1.3 milliseconds then the primary winding duty cycle is 79%. 100-(1.3/6.2*100) A 3 ohm resistance at 13 volts draws 4 amps (13 volts / 3 ohms). I’m simply having difficulty understanding how a 1 second power toggle could harm the primary winding.

As an amateur radio operator I am kicking myself for not realizing a coil and a capacitor in parallel is a resonate circuit.

I'm learning stuff.... reading up on a little Honda I just got, has points and condenser ignition..... you need the condenser if you're direct like all your hookups.... electronic ignition systems can eliminate both or as one guy has developed.... keep the points and eliminate the condensers.
As for resistance, if you have resistor plugs you don't need resistor caps, but 5 k resistor caps can be used with resistor plugs, and must be used with non-resistor plugs.... or so I'm reading. The resistors just keep the static offa yer AM radio.

N4HHE wrote: ↑Fri Jun 14, 2024 8:30 pm As an amateur radio operator I am kicking myself for not realizing a coil and a capacitor in parallel is a resonate circuit.

Reading, this is an LC Tank circuit? How does this impact, or does it affect the wasted spark test config on my bench? Thanks in Advance, learning.

raYzerman wrote: ↑Fri Jun 14, 2024 10:18 pm I'm learning stuff.... reading up on a little Honda I just got, has points and condenser ignition..... you need the condenser if you're direct like all your hookups.... electronic ignition systems can eliminate both or as one guy has developed.... keep the points and eliminate the condensers.
As for resistance, if you have resistor plugs you don't need resistor caps, but 5 k resistor caps can be used with resistor plugs, and must be used with non-resistor plugs.... or so I'm reading. The resistors just keep the static offa yer AM radio.

Yeah, me too. Been YEARS since I studied DC/AC theory in JC. Forgot most of it. Yes, these are resistor plugs.
Here's a good video showing the impact the condenser has to save points.
https://youtu.be/MQtMtvf5a4E

D

So essentially you need the condenser in your test setup..... now for the switching, maybe fab up a plate with a set of points and a hex nut for a cam to operate them? Or find an old distributor...... however, what do you need to know at this point, the coils are working!

Yes, it looks like coils are working so not the problem. Are the coils getting good voltage on the bike? Is it Battery or Magneto ignition system?

raYzerman wrote: ↑Sat Jun 15, 2024 8:12 pm So essentially you need the condenser in your test setup..... now for the switching, maybe fab up a plate with a set of points and a hex nut for a cam to operate them? Or find an old distributor...... however, what do you need to know at this point, the coils are working!

I found this coil tester and ordered it. It also can test most any device requiring a pulse. Stepper motors, fuel injectors, etc.
https://www.amazon.com/gp/product/B0CZ8 ... UTF8&psc=1

Road Runner wrote: ↑Sun Jun 16, 2024 7:21 am Yes, it looks like coils are working so not the problem. Are the coils getting good voltage on the bike? Is it Battery or Magneto ignition system?

When battery is at 13.8, coils are seeing 13.5. Coil resistances are matched to keep the ignitor (3 Darlington transistors) happy. Also performed the FSM pick up coil test, all 3 are SAT. Did read where one guy sent power direct from key on relay to coils for max voltage. His other option was replace the 45 year old wiring harness which is $$$.

Can't wait for the tester to get here!

Maybe your spark is fine and something else is wrong.
What are symptoms?

Road Runner wrote: ↑Sun Jun 16, 2024 2:43 pm Maybe your spark is fine and something else is wrong.
What are symptoms?

The bike runs, but sputters and is missing. Carbs were professionally rebuilt (although should have done them myself, in hindsight).

Installed new ignition aftermarket coils which eliminated the ballast resistor which is a known failure point that will burn out the Ignitor module.

When I place the plugs on the cylinder head and crank, I have very little visible spark.. As in, are they sparking? Cover to help eliminate daylight, still can't really tell if spark is there. As compared to my FJR's where I can easily see spark, even in direct daylight.

dcarver wrote: ↑Sun Jun 16, 2024 3:54 pm

Road Runner wrote: ↑Sun Jun 16, 2024 2:43 pm Maybe your spark is fine and something else is wrong.
What are symptoms?

The bike runs, but sputters and is missing. Carbs were professionally rebuilt (although should have done them myself, in hindsight).

Installed new ignition aftermarket coils which eliminated the ballast resistor which is a known failure point that will burn out the Ignitor module.

When I place the plugs on the cylinder head and crank, I have very little visible spark.. As in, are they sparking? Cover to help eliminate daylight, still can't really tell if spark is there. As compared to my FJR's where I can easily see spark, even in direct daylight.

Are the plug wires and ends OK?
Did swapping the coils make any difference?

Road Runner wrote: ↑Sun Jun 16, 2024 9:31 pm

dcarver wrote: ↑Sun Jun 16, 2024 3:54 pm

Road Runner wrote: ↑Sun Jun 16, 2024 2:43 pm Maybe your spark is fine and something else is wrong.
What are symptoms?

The bike runs, but sputters and is missing. Carbs were professionally rebuilt (although should have done them myself, in hindsight).

Installed new ignition aftermarket coils which eliminated the ballast resistor which is a known failure point that will burn out the Ignitor module.

When I place the plugs on the cylinder head and crank, I have very little visible spark.. As in, are they sparking? Cover to help eliminate daylight, still can't really tell if spark is there. As compared to my FJR's where I can easily see spark, even in direct daylight.

Are the plug wires and ends OK?
Did swapping the coils make any difference?

Bike was running with old Martek aftermarket coils. Bought new coils from YellowSquare. New wires, new caps, new plugs. The new coil allowed eliminating the ballast resistor, a known failure point. With new coils, bike ran good for about 30 seconds then started bucking and farting. That's when I checked for spark and found very weak spark.

Does it run good with old coils? If so, there's the problem. If not, then need to dig further. Then ohm check charge coils, trigger coils, Ignition coils.

You mention the KZ has igniters... I don't know anything about igniters, but had them on my old Magna, and bought spare set. Any spares to play with? These days, aftermarket replacements might be available.
And perhaps put your old coils to the test setup you had, see if they sparkie well, then perhaps the bike's system is the issue?