Dyna Coil question

Okay, I am not new to coils, but this one has me a little confused.

I have less than one year old Dyna (3 ohm) dual output coils installed on my '79 KZ650B3 with a Dyna S ignition. Today I went out to finish up a few things in the garage, so I wheeled it outside and was going to run it for a few minutes while I moved a few things around. The bike fired right up, but was idling very rough.

After checking the timing (which was dead on) and the plugs, I noticed that 3 out of the 4 plugs were nice and tan, but the #2 plug was wet and black. So, I checked the spark on that plug, nothing. Checked the spark on #3, big fat spark. I grabbed a spare plug thinking that maybe the plug was fouled, still nothing. This got me thinking, so I moved the plug wire that was on #3 to the #2 port, used the plug that I knew worked on #3, NO SPARK!! For giggles, I moved the plug that was on the #2 port to #3, big fat spark!!! That tells me its not the wire, or the plug.

Is it possible for only one port to fail on these dual output coils? They are less than a year old, and the bike was running great less than a week ago!! Never seen this before, so I thought I'd ask before I dropped more money on coils.

Both spark plugs are included in the secondary loop.
A break in the loop means no high intensity voltage passing through the loop, whereby neither plug with fire.

Are plug wires also relatively new Dynas with built in caps?
Is voltage leaking from secondary loop?

Maybe the caps are going bad, or there's weak connection somewhere in the loop at coil>wire>cap>plug>plug>cap>wire>coil .

If the coil will fire one spark plug, it should also fire the other spark plug.

[Click on image to enlarge view.]



Good Fortune!

Hmm, I guess now I am really confused then. Even if I disconnect the plug from the port for #3 cyclinder (completely remove it) I get no spark on #2. But if I move the plug wire from #2 to the port for #3, I get a spark. I am leaving the plug in the same place on the engine, soooo something is not adding up here. Based on your diagram, if one plug wire is completely removed from the circuit, that means that the plug can't/shouldn't fire, as there isn't a complete loop... But it does......

It doesn't make sense UNLESS each plug has an individual secondary winding, creating individual loops for each wire?
Maybe one side failed? AARRGGHH, I hate electrical...

Did you check to see you have a nice fat spark on the three of the four plugs? You havent left the ign on for more than a few minutes?

kzconvert_86 wrote:

Hmm, I guess now I am really confused then. Even if I disconnect the plug from the port for #3 cyclinder (completely remove it) I get no spark on #2. But if I move the plug wire from #2 to the port for #3, I get a spark. I am leaving the plug in the same place on the engine, soooo something is not adding up here. Based on your diagram, if one plug wire is completely removed from the circuit, that means that the plug can't/shouldn't fire, as there isn't a complete loop... But it does......

It doesn't make sense UNLESS each plug has an individual secondary winding, creating individual loops for each wire?
Maybe one side failed? AARRGGHH, I hate electrical...

nevermind.

Lemo, yes, the 3 other plugs all have nice fat sparks. I have even switched the wires to the different ports IE,


When I say port, I mean the port on the actual coils:

#2 wire -> #3 port = The plug fires(plug that came from #2)

#3 wire -> #2 port = The plug does not fire (used plug from #3, which I know works)

I have also swapped the plugs between the wires with the same results. I had some spare wires hanging about, so I put those on and repeated the test, exact same results....

reverse your dyna leads and see if problem moves to a different coil bank.

A different test --
Remove center plugs and tape (or rubber band) them together.
Plugs need not contact engine.
Spin engine over as if starting normally.
Both plugs should spark.
If not, re-test using brand new plugs.
If only one plug sparks, would guess the non-sparking plug is somehow internally shorted and allowing current to pass through without jumping the gap. Or through a shorting plug wire.

Old hard cracked worn out leaking plug wires cause strange things to happen, what with current escaping to ground via the engine head, frame or metal fittings. This might permit closure of the secondary loop without needing to pass through both plugs. (More about this phenomenon in a following post).

[Click on image to enlarge view.]



Good Fortune!

Pretend the plugs are #2 and #3 instead of #1 and #4.

Probably should have mentioned this, the plug wires are all brand new (as of 20 minutes ago), and I have now replaced all the plugs with my spares, also brand new.

Lemo, I tried that just a few minutes ago, no change whatsoever.

Also, I tried something with the trusty multimeter. Turned it to voltage, and put on lead directly into the wire port for #2, touching the other lead to the head. When turning the engine over, VERY low output, barely hit 100. Repeated the test on the other port (#3), voltage was off the charts.

Patton, I'll give that a try and post the results.

Another test for high intensity wiring is to spray water mist over the wiring while the engine is running in a dark garage.

Watch for sparks.

Dyna plug wires are inexpensive and available at Z1E.
They already have the caps permanently attached.

Would recommend solid core unless radio interference would be an issue.

Good Fortune!

kzconvert_86 wrote:

...plug wires are all brand new...all the plugs...also brand new...
Also, I tried something with the trusty multimeter. Turned it to voltage, and put on lead directly into the wire port for #2, touching the other lead to the head. When turning the engine over, VERY low output, barely hit 100. Repeated the test on the other port (#3), voltage was off the charts....

What happens if this is done on the other coil?