OK, here goes…..
FACT. Electricity follows the path of least resistance.
Fact: when time to fire, the voltage in the coil secondary starts at zero and rapidly rises until it is finds a lowest-resistance path to ground Then it arcs to ground via that path and the energy dissipates and it starts all over again till next time. Hopefully, that path of lowest resistance is through the plug wires to and across the plug gaps.
Fact: Those old mags were capable of producing possibly 50 K-volts.
Fact: The path thru the plug gaps might require only 30 K-volts to fire, or whatever, according to gap width, temperature, compression pressure, etc. So, it actually only needs 30 K-volts (or whatever) to run.
Fact: We are so programmed in our heads to look for that magical “fat blue spark”, so if it will produce that magical fat blue spark we assume everything is ok.
Fact: For whatever reason, Johnson decided to limit the coil output to something a bit over the actual voltage needed to run I suppose to protect the coils from over-volage, When built, those mags had L-shaped “teaser” brackets near the soldered connection. If the voltage is to high, the spark jumps to the teaser bracket and is dissipated. OR, if somebody has removed the teaser brackets, it looks for the next-lowest path of resistance, likely to the coil mounting screw.
Which brings us to the conclusion: If it is arcing to the screw, the voltage is way beyond what is necessary to fire the plug. The mag is ok, in fact better than it has to be, and is not broken, and doesn’t need fixing.
Frank,
Thank you. Lots of good information. I don’t remember the name, but Johnson had a name for the ‘teaser’ didn’t they? I think it was called the Maverick system?
I understood everything you said and it all makes sense, sort of.
To clarify, you are saying that it is okay that I could not achieve greater than 1/8″ spark gap in the spark tester?
The even bigger question is that while testing via the spark tester, when a I open the gap more than 1/8″ is when the coil shoots the voltage to the laminates. Your saying that won’t/shouldn’t happen under true running conditions?
I realize that the plug gap of .030, ~1/32″ is much smaller than 1/8″ and should fire before the solder joint to laminate BUT it is admittedly hard to ignore the repeated edict that ‘solid blue spark at least 1/4″ is necessary”.
In your opinion the mag plate, as built (pulled it off the motor and built brand new one) previously would likely be enough to run the motor?
I appreciate the wealth of information. I really liked your approach (LOL), “FACT”. Kinda makes one pay full attention to the words on the page.
Please let me know what you think?
Try and get better. It sucks to be sick when trying to work. I appreciate you taking the time today, even sick, to help out.
Best Regards,
John Gragg
RIverside, CA
Just starting in the hobby, please be patient.
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