Dyna Ignition Problem

[Duane Ausherman]

We always tried to get it all set up to "very close" before even starting the engine. I have been burned a few times, but I learn to keep my skin away from hot things. I mean hot things on the motorcycle.

[presidentcamacho]

Been a busy winter but returning to this problem now. It starts up fine when cold. Plenty of spark but if I ride for a while, shut down, then try to start up again there is no spark on either plug. 15-20 minutes later after the bike has cooled off a bit, it will start again. What could cause the Dyna to not spark when the engine is hot? Could it be a battery issue? Is is possible that the battery is somehow getting hot and not putting out enough voltage? If so, what would cause that?

[Bamboo812]

The intermittent failure while hot is a common symptom of a coil going bad.

[presidentcamacho]

Thanks for your input.
A couple of things...
As long as the engine is running, it is not cutting out. Instead, if I turn the engine off, it won't start back up again until it sits for a while. Also, I am getting the same symptoms on both sides. It will spark once, maybe twice then nothing. Would this mean both coils are going bad or would one coil going bad somehow effect both plugs?

[Ken in Oklahoma]

The intermittent failure while hot is a common symptom of a coil going bad.

For those who might not know, the prime reason that coils go intermittent is that the windings inside the coil are going bad. Those who have been inside a coil know that there are lots of windings of very fine wire, particularly in the secondary windings. As coils are used they heat up and cool down every time the coil is used. This causes the copper windings to 'squirm' around and rub against each other. They can fail in two ways, either with the coil winging going open circuit or the windings rubbing against adjacent windings and rubbing the insulation away. The insulation of the windings is a very thin 'varnish' which can and does degrade with use and heat.

The reason the coil starts working again is that when it cools down the shorting windings move around and are no longer shorted. Or, if the windings had opened, the cooling of the coil will allow the open ends of the winding to touch ends again.

On two occasions I have chased my tail trying to fault isolate coils for sure. After I work on the bike it will start fine, but did I really fix the problem. Plus there is the specter of getting stranded on the road.

For this reason I always keep a set of new coils in stock. They are expensive, but so is the stress of trying to trouble shoot coils.

By the way for those who don't know, bench testing coils is risky at best. A good spark means little. A spark is much easier to produce at atmospheric pressure than it is under real world compression pressures.

Ken

Editing, if not the coils the problem could easily be the electronics box of the Dyna Ignition. Those of you who have paid attention to my rants know that they are invariably about the Dyna Ignition. Sorry, couldn't help myself again.

[Major Softie]

Editing, if not the coils the problem could easily be the electronics box of the Dyna Ignition. Those of you who have paid attention to my rants know that they are invariably about the Dyna Ignition. Sorry, couldn't help myself again.

Yes. Electronic ignition boxes are just as susceptible to failure-when-hot as coils are.

[SteveD]

It starts up fine when cold. Plenty of spark but if I ride for a while, shut down, then try to start up again there is no spark on either plug. 15-20 minutes later after the bike has cooled off a bit, it will start again.

Exact same problem my Moto Guzzi LeMans mk2 had. It had a Piranha EI added. The starter motor on the Guzzi was down by the gear change, so I would just lean down with a screwdriver and short the starter to make it go. Not quite as easy to do on the beemer.
I'd be looking at the dyna.

[bbelk]

Electronic ignition boxes are just as susceptible to failure-when-hot as coils are.

Failure maybe, but Electronics either works or doesn't work. Coils can actually keep working with varying degrees of goodness making problem identification difficult. If something shorts in an electronics box, the box just quits working. A turn to turn fault in a coil just removes one turn out of hundreds and you hardly notice the degradation.

[Major Softie]

Electronic ignition boxes are just as susceptible to failure-when-hot as coils are.

Failure maybe, but Electronics either works or doesn't work. Coils can actually keep working with varying degrees of goodness making problem identification difficult. If something shorts in an electronics box, the box just quits working. A turn to turn fault in a coil just removes one turn out of hundreds and you hardly notice the degradation.

True. Black box failures are almost always one type: total failure. They may come back when cooled off, but when they aren't working, they don't work at all. Coils can have all sorts of weird gradual degradation.

My Honda Ascot is kind of famous for coil failure (they last around 20 years - not that shabby - but then they all fail). They all seem to follow the same pattern: weaker and weaker spark when hot, until they start to behave like bad diaphragms when hot - they just won't go over 4000 rpm or so. It' really easy to diagnose though: if you pull the plugs and close up the gap smaller than spec, and the bike runs way better, then you know it's the coils.

[presidentcamacho]

OK, Sounds like my best bet for diagnosis is to see if anyone in the area has some spare coils I can borrow...or if not just buy some cheap used ones on ebay. If that does not solve the problem then it is likely the Dyna box. I emailed support at Dyna and they suggested checking the ground (had already done that) and checking the battery voltage when hot (will do that this evening).