Dyna III question

[obray]

I have an '83 LM III, with a Dyna III ignition. It has been on the bike for the last 18 years I've owned it. Recently it has exhibited a rare, quick, cutting out which lasted no longer than a second, but was noticeable. This progressed a few weekends ago to what seemed to be a total ignition failure. The first time it died, I pulled over and waited 10 or so minutes, and then it fired up again. I rode for about another 10 minutes and it died in the same fashion. Trucked home after that..

My question(s) is: given that there are two coils, two pickups with the Dyna, and given that the pickups fail
usually individually, how might I diagnose this? Obviously checking wires and connections are first, but it seems
a single bad pickup is out of the question, as well as coil. Is there a history of intermittent impending doom
of the Dyna? And then total failure? I have not heard of this before....


Rob

 

[Tonerjockey]

Hey Rob,

I used a Dyna III on my race bike and have never had a problem that I know of.

Here's the schematic:

Let's review how this thing wokrs a bit:

The controller (black box, cloud, do-hicky) provides a ground path for current from each coil in a timely manner. The distributor has two Hall Effect sensors that are triggered by the rotating magnet. When the sensor senses the magnet the Hall Effect sensor allows current to flow (grounding). The controller senses this and grounds a lead from either coil ... this collapses the field in the coil and viola ya get thousands of volts of potential (hopefully) out of the coil.

The red wire W/O the intermediate connector goes to the right cyl. providing a controlled ground path for the right coil. The green wire provides the ground path for the left cyl. If one of these connectors was bad only 1 cyl would misfire. Let's rule these two wires out.

The red wire with the intermediate connector provides power to the controller and the Hall Effect sensors in the distributor. This wire is a candidate. If it were to fail (break, burn, get pinched, fall off etc) the ignition system would fail.

The white wires to the coils provide 12V to the coils... This white wire, since it is common to both coils, could be bad. Another candidate.

In this cartoon above there is a blue/black wire between coils. Since the green wire is AFTER the blue/black (in current direction so to speak), it too could cause a total failure.

The black, white, and red wires from the controller to the distributor contain power for the Hall Effect sensors in the distributor and signal back to the controller. Grounding is provided by contact under the distributor plate to the distributor housing.

Bad grounding in the distributor would affect entire system... highly unlikely IMHO.

The white and black wires to the distributor carry the right and left signal (ground path) respectively. The red wire is power to the plate. Let's rule out the white and black wires (they only affect 1 cyl @). Failure of the red wire from the controller would cause total failure in the system.

If the grounding wire ("not to frame") fails, so too with the system probably.

If the controller failes (over heating, shock, old age etc) so goes the system.

And finally, the rotating magnet and mechanical distributor could fail.... unlikely IMHO.

So, we have:

Red wire with intermediate connector, from controller to coil
White to coil
Blue/Black between coils (mine is not that color combination)
Red wire in 3-wire bundle to distributor
Black ground wire
Controller

Check the wires visually. I would avoid a DVM (digital volt meter) as I am unsure of the sensitivity of the controller.

Good luck

Alex

 

[Tonerjockey]

Oh yeah I forgot to mention the 3 wires from the controller to the distributor have unusually crappy connectors. Check those as they are the most likely candidate to me.

Make sure all connectors are CLEAN and secure.

Alex

 

[guzzigray]

http://www.dynaonline.com/skins/downloads/

There's a trouble shooting guide at the above link from the Dyna site.

Check grounds. If that doesn't work I would buy a new unit. New Dyna's are pretty cheap.

Also if you have 3 ohm coils you might think about upgrading to the black 5 ohm items. Dyna recommends them now.

Good luck.

 

[mwest]

I had almost identical symptoms on my LMIV. Turned out to be a bad connector for the dyna power. If you see connectors that look to have a clear vinyl jacketing over them, cut them off and put new ones on.

These connectors start as 2 pieces, the barrel that gets crimped to the wire and the actual lug. After the barrel is crimped, they use some kind of adhesive to attach the lug. Over time, oxidation builds up and it becomes intermittent and eventually dies altogether. Mine died on me several times only to start again after sitting for some time. Then one day it died and didn't start. Then it was easy to troubleshoot.

A few months after I fixed that, the same problem occured and it turned out the same type of crappy crimp was used on the ground lug. stupid me for not checking that when I fixed the hot wire. It's been a couple years and 10k miles or so since and no more ignition problems.

Heres what my ground lug looked like after the two pieces fell apart after cutting off the insulation.