Dyna coil failure...overcharging system?

I have had a set of Dyna coils (and Dyna S) on my 77 KZ1000 for the last four thousand miles or so. Driving home the other day, I suddenly lost two cylinders. I pulled all the plugs and engaged the starter, and sure enough just the 1 and 4 plugs have spark. Took the tank off and pulled the wires to the dead coil, and the connectors are oily and have green corrosion. The number four wire on the other coil is oily and a little green too, but that one was still firing. There is no visible cracks on the outsides of the coils. I can only assume that my regulator is bad and I am getting way too much voltage. Any input would be greatly appreciated!

Should be close or 100% the same a the 76 KZ900... Someone else can chime in if incorrect...

EDIT: Removed Image.... :pinch: :pinch: :pinch: :whistle:

Thanks for the info! Hopefully she'll still be in the mood to start and run well enough on 2 cylinders to do the test!

Coils, Dynamo and Rectifier can be checked with DVM (resistance measurements)...

Granted, not as good as running but if severely damaged, dead short, open etc... the meter will detect this....

I don't think that higher voltage would hurt the coils. My new MSD ignition pumps 400 Volts into the coils.

otakar wrote:

I don't think that higher voltage would hurt the coils. My new MSD ignition pumps 400 Volts into the coils.

What the... ??? Why?

400 Volts... what kind of amperage?

:huh:

The Green Dyna 3 ohm coil(and maybe the other Dyna coils) use a 10-32 x 5/16" long screw.

If the supplied screws are too lost and replacements are used they maybe too long, they will bottom out before the screw gets tight.

Do you live in a humid,salty environment? Are the wires going to the coil properly crimped? I'd suggest checking the wiring for insulation damage too.

Did you switch the wires from the Dyna S to the coils around to verify that it is actually a bad coil? The Dyna S does have a tendency to go bad on just one side.

Old Man Rock wrote:

Pretty hard to get that starter to turn with a 20A fuse in the positive battery cable. :blink: :laugh:

TeK9iNe wrote:

otakar wrote:

I don't think that higher voltage would hurt the coils. My new MSD ignition pumps 400 Volts into the coils.

What the... ??? Why?

400 Volts... what kind of amperage?

:huh:

It's CDI. CDI systems hit the coils with a big spike of voltage. The coil just acts like a transformer unlike in a standard KZ ignition where it actually stores energy.

However, the coils in the standard KZ ignition also get a spike of several hundred volts on them right when the points open, or right when the igniter lifts the ground side of the coil.

In CDI, the module generates the high voltage, in standard (Kettering) ignition, the coil generates the high voltage. Both of these are on the primary side of the coil. The coil steps up this several hundred volt spike into several thousands of volts at the plugs.

After the spark initiates, the voltage (on primary and high-tension side) drops to a much lower level.

If the charging system is faulty and allowing the battery voltage to get too high, the coils will be able to stand the voltage, but the extra voltage causes more current, which causes more heat, and that is what can cook the coils.

With MSD or any CDI, the current is only in a super short pulse so there is no real heat issue to worry about. (Dyna S is electronic Kettering, not CDI.)