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.


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…


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


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:


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


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.