Dyna-III failure -NOT - Maybe solved

[pehayes]

My SPII has a Dyna-III ignition.  It has been rock steady for years.  Suddenly now it won't spark.  I still have the original points plate but I'd really hate to put that back in.

When I turn the key to off or the drop the kill switch, I get one spark zap as indicated by a strobe light flash with an inductive pickup on the secondary wire.  Does that on both cylinders.  That tells me that the plug, wire, coils, and Dyna amplifier are all working properly.    Thus, it would seem to be in the triggering system and not the amplifier/spark system.  I'll dig into the distributor to look at sensor gaps, rotor, etc.  Anything else that is generally problematic?

Patrick Hayes
Fremont CA

[Aaron D.]

All I've ever found were bad solder connections.

[ccoli]

I got a box of dynamic parts. Wish I knew which  its work and which don't. I  can post them to you and you can play parts swapper. 

[bigbikerrick]

                                                           

This topic is interesting to me as I have a Dyna III in both my Cal II, and Lemans IV.
Rick

[azguzzirep]

When I had a problem with mine, I mailed it to the Dyna corp. (I called first).

This was a long time ago and I don't remember if they repaired it or sent me another one ($$) but I was happy to have my bike fixed.

Patrick. I  think DynaCorp is in CA.

Tom

[rodekyll]

I had one fail, called dyna for troubleshooting support, and they replaced it in the course of the support call.  The unit was easily 7+ years old and I had not called for a replacement -- the support guy offered it.  That has been a lot of years ago, but I was impressed that they volunteered to take responsibility for a failed electrical component after so many years and miles.  I hope they're still that way.

[pehayes]

After a longer assault on testing, I have confirmed that the Dyna-3 is just fine, thank you.  It turns out that I have two other problems which caused the faulty diagnosis.

Problem #1 - I use a self-powered inductive timing light clamped to the spark secondary wires to detect spark activity.  Sometimes it fired, sometimes not, sometimes once and then nothing.  As it turns out, there was crappy internal contact in the momentary switching of the tool!  DOH!  Cured that and now the light fires reliably.

Problem #2 - Not firing again.  What????  Turns out if I test the right cylinder it fires reliably.  Any prior intermittent function was due to #1 above.  Testing the left cylinder zilch.  Next, clamp a spark plug to the head guard metal and the left cylinder now fires repeatedly.  What????  Switch back to the installed spark plug and firing fails.  What????  Swap the installed plug out and the known good plug in and the firing fails again. What????  Test the failed spark plug clamped to the head guard metal and it fires repeatedly.

So, I think I have now verified one VERY weak ignition coil.  It works fine at atmospheric pressure, but refuses to spark the gap when 10:1 compressed air is involved.  It is a known phenomenon that it takes more electrical power to jump a gap when under compression.  Replacement coils on the way.  Stand by for future results.

Patrick Hayes
Fremont CA

[wymple]

I have Dyna S on my Cal II since 1992, and on my son's V65 since 1988.  Never a problem with them. Good stuff.

[jrt]

So, I think I have now verified one VERY weak ignition coil.  It works fine at atmospheric pressure, but refuses to spark the gap when 10:1 compressed air is involved.  It is a known phenomenon that it takes more electrical power to jump a gap when under compression.  Replacement coils on the way.  Stand by for future results.

Seriously?  I think I just learned something.  Thanks Patrick!

[pehayes]

Seriously?  I think I just learned something.  Thanks Patrick!

I had heard of such a theory.  Google search leads to plenty of confirming discussion.  Compressed air/fuel in the spark plug gap makes electrical resistance to sparking much higher.  Thus, if there is any other weakness like a faulty coil or faulty secondary wire then the spark energy leaks out elsewhere instead of jumping the plug gap.  Fortunately I had another old secondary wire to substitute and got the exact same results.  I conclude it is a bad coil.  I suppose it could be TWO bad secondary wires but my bet is the coil.

Patrick  Hayes
Fremont CA

[Aaron D.]

I've seen it before-in the days when points were the only way to spark.

[John A]

Aviation spark plug testers feature a pressure chamber that the plug goes in and hook up to shop air, about 80 psi. Plugs that fire under atmospheric sometimes don't under pressure, and then are junk.

[Triple Jim]

I found that it's about a 5:1 gap ratio.  A 5mm gap in the shop is about like a 1mm gap in a running engine, so I test the CDI units I build with my "special" spark plugs.  I cut off the ground electrode and use the lathe to turn back the steel body of the plug until there's a 5mm gap.  The conditions still aren't identical to an engine, but it makes a valid go/no-go test to make sure the ignition units are up to spec.

I didn't arbitrarily choose the 5:1 ratio.  Years ago I built a prototype CDI unit, and a beta tester was trying it in his motorcycle.  He found that at 10,000 rpm, which was 30,000 sparks per minute, it was starting to misfire.  I started opening up a spark plug's gap more and more until I duplicated the misfire at that speed.  I was able to make changes to the electronics to work correctly at 30,000 sparks per minute, and I've been using the 5mm gap for testing ever since.

[bigbikerrick]

Hi Patrick, Im curious, what coils did you decide to purchase? I need to replace the  30 y/o coils on my Cal II with Dyna III.
Rick.

[jrt]

Wow, that's very interesting.  I would have guessed that it should be easier to spark under pressure.  After all, the electrons pass through gas molecules to make a spark and there should be more gas molecules per unit area under high pressure. 
I wonder what's going on? 

[ITSec]

Wow, that's very interesting.  I would have guessed that it should be easier to spark under pressure.  After all, the electrons pass through gas molecules to make a spark and there should be more gas molecules per unit area under high pressure. 
I wonder what's going on?

(Dragging out my physics from university...)

If you think if the charge as moving along the outer electron shells of the molecules between the electrode points, then fewer molecules means a faster, easier transfer. The energy needed to jump from the shell of one molecule to the next is the controlling factor, not the number of shells available for use. Fewer shells means less energy for the transfer over all, as fewer jumps are needed. Another reason why lightning doesn't happen in water 

[charlie b]

Hi Patrick, Im curious, what coils did you decide to purchase? I need to replace the  30 y/o coils on my Cal II with Dyna III.
Rick.

I just use 60's VW/BMW coils on my Dyna III setup.

[Triple Jim]

Charlie, are those the Bosch Blue coils?  I've been using those for a couple years now.  They perform great, are oil-filled for longevity, and are inexpensive.

[rodekyll]

Wow, that's very interesting.  I would have guessed that it should be easier to spark under pressure.  After all, the electrons pass through gas molecules to make a spark and there should be more gas molecules per unit area under high pressure. 
I wonder what's going on?

Gas has nothing to do with the spark.the spark is electrons jumping a gap.  When. gas gets involved one of two things happen : either the gas goes bang or it quenches the spark.  Electricity Is lazy stuff.  It would rather flow than jump, but it would really rather take a nap.  That's what the law of conservationof mass/ energy is really about.  But seriously, the nature of else trons is to take the path of least resistence.  That means it will only jump the plug gap if
1) there is sufficient strength to the charge, and
2) there is no easier path to ground

[ITSec]

Gas has nothing to do with the spark.the spark is electrons jumping a gap.  When. gas gets involved one of two things happen : either the gas goes bang or it quenches the spark.  Electricity Is lazy stuff.  It would rather flow than jump, but it would really rather take a nap.  That's what the law of conservationof mass/ energy is really about.  But seriously, the nature of else trons is to take the path of least resistence.  That means it will only jump the plug gap if
1) there is sufficient strength to the charge, and
2) there is no easier path to ground

There's gas (fuel) and gas (stuff with too little density to be liquid) and gas (stuff we all output in physical and verbal forms)!