Ignition systems

Ok, a little follow up on my coil modification.


The re-wind coil get a outer layer of electrical insulation tape.

And then a layer of textile reinforced tape, this is ok because this coil is only low tension by now (this textile tape could collect some moisture). I prefer big heat-shrink tubing, but couldn’t find any in my stuff.

Coil in place, some rubber-shoe sole repair glue keeps the wires steady in the coil ends.

The enameled copper wire needs thorough cleaning, easiest is to heat it with a cigarette lighter, and scrape off the burned enamel.
The left side wire is soldered together with the orange wire, and connected to the condenser/points.
The orange wire is wired to the outside coil +.

The other end is cleaned, and grounded, this is often soldered to the coil core, in this case connected to a ground screw.

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Next steps, separate coils could be found cheap, they are sturdier, because they dont have the space limitations as a flywheel coil.


Separate/freestanding coil, with 2 terminals, marking + and -, mostly they have no markings, in that case, no matter how they are connected.
With only one terminal, coil is grounded through the core.

Now to the sad part: i forgot to snap a pic of how i mounted the coil, i tend to get a little excited when it comes to get old stuff running, sorry :pensive:
So, i put the flywheel, and the shroud back before i remembered.
Anyways it’s located below the flywheel and magneto, bolted in one of the intake bolts, and grounded in the same.
A short piece of high tension plug wire, to the plug.


Time for test: dmn! Has anyone tried to photo a ignition spark? Not the easiest, but i got it after some attempts.
I used a spring-clamp to hold the plug, im not very found of the “tickling sensation” that could be the case when testing spark.

And: Finally! It runs! This must be the machine from :smiling_imp:
***, it thinks it’s some kind of jet-powered pogo stick, i felt like Wile e Coyote (he thats never gets the Road-runner) it jumps up and down, and shakes, until it revs up, then it behaves more like a rock-drill.
And the sound! The roar coming from the straight 1 3/4" exhaust sounds more like a ,50cal machine gun… and the smoke… well, i guess i start it outdoors next time.

This is the Hand-crank starting device, very nice when it back-fires, really don’t want to loose the grip then, and got hit on the wrist, which even happens if i stop it, whit the crank in place, it’s last breath seems to go backwards…

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göran, great work!! it would be urgently needed a kind of webcam in your workshop to see all what you construct !!

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Goran, excellent work, how do you think the power of the spark?
The old Cobra is again ready for action, drilling, breaking and “torturing” a person, an hour of work with this machine is a better training than an afternoon at the gym. :+1::grin:

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Thanks Giorgio :slightly_smiling_face:
A webcam? Well that would be some fun :thinking:

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Thanks Tone, i haven’t “analyzed” the spark, only with my senses, it’s a “fat” blue spark, and if i turn it slowly i can hear the spark snap.
With original coil the spark was thinner, pale, and no “snap” it managed 7mm in my spark-tester though, and that would be sufficient.
Well, i believe the old coil shorted when the voltage raised, when the motor fired and started turn faster, not unusual on old machines.
And yes, this machine is a beast, i prefer the Cobra when it comes to real working, this oldtimer, made 1938, is more of a museum piece, i still going to use it though.

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