Dual plugged Dyna 3 R90S, no spark

[ludditer90s]

Okay.."senior moment" last weekend, left the ignition on for 4 hours-- warned about that many moons ago by an author/guru (Tom Cutter?) turning my Dyna3 ignition coils to black goo, on my dual plugged beloved '75 R90S.
So, replaced coils with new 3.0 ohm coils (same), still no spark.
No wire melting anywhere other than cooked and cracked coils. Replace Dyna 3 module?
Cannont find anything on Snowbum site....
Halp!
Cheers!
Bob Kennedy, Sandy Eggo, CA
R100rs "Goldie" you saw her at the WY Rally '08
R90S "Bertha" hot rod I talian pistons, hot cam, 2 into 1 Luftie

[20774]

Still running points? You should probably investigate the ignition system step by step.

- do points open and close properly
- points open/closing results in 12v along the path to the coils; use an ohmeter to find out where that 12v is lost
- try turning ignition on, points closed. With a spark plug stuck in a high tension lead and threads grounded on the cylinder fins, what happens when you carefully open the points with your fingers? It should spark the plug. If not, then go back down the path to the coils, module, points, until you find where the energy is lost.

[ludditer90s]

No, no points. Electronic.

[20774]

Well, you still need to see a 12v transition at the coils in order for the spark to happen. I have a Dyna III electronic ignition system on my /7 but it just operates the same way (essentially) as the old points did. During part of the rotation of the engine, the coils see 12v. Once the trigger mechanism in at the Dyna plate determines it's time, the "point" open and the 12v at the coil disappears. When that disappears, the field collapses in the coil and you get the high energy release down the spark plug wire.

So, you should investigate if that is happening. If you don't see 12v transitions at the coil, then you have to work backwards to find out what part of the system is not switching.

Sorry, that's not much help, but in reality it's a simple system, just complicated by "expensive" boxes along the way. At some point, you'll find a box isn't working or that a wire is not grounded or something...