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The separate coil ground wire issue.

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34nineteen

34nineteen

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Mar 6, 2015
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Kolache Factory
This is interesting. Many people have commented that their bike runs better when the coil has an auxiliary ground wire to the battery. However, according to the service manual (2004 XBS), on page 4-99 it states the “coil will function without being attached to the frame”.

So, is this wire actually solving an issue or is it a bandaid for ground maintenance???

Discuss...
 
Its all an illusion! Haha
An ignition coil does not need a ground on the chassis to operate. In fact, if anything in that primary circuit was connected to ground, the coil would not work at all, and your ignition fuse would blow.

The "coil" is one wire (primary) coiled around another winding (secondary) thats coiled around an iron core. The (-) that makes that circuit is the spark plug threads on the other side of the electrode gap. Thats the only way you get spark across that gap. If you put the secondary windings to ground = no spark.

The (+) charge on the windings wrapped around the iron core make a magnetic field. It is the act of the (-) signal from the ignition that causes the magnetic field to collapse and shoots the voltage out of the secondary windings at a drastically higher number.

By grounding the chassis of the coil, maybe you can reduce some ignition noise (the magnetic field collapsing every time a plug fires) but it won't give a bigger spark or anything silly like that. But hey, whatever makes people feel good ya know?
 
Wait, what? The coil needs to a complete circuit on the primary side to energize it. Once you open the connection, the field collapses and transfers to the secondary side through induction. Then the high voltage goes through the HT leads to ground. But you have to have a ground on the primary side. The part you don’t need is a positive source for the secondary since it gets that from the primary.

Just because the circuit is complete doesn’t mean the fuse will blow. The coil (primary) is creating a load, like a light bulb. However just like back in the points days, if your distributor stopped with the points closed you could burn up a set of points if you left the ignition in the ON (not ACC) position. Been there, done that while making out with my GF back in my HS days in my Porsche 914.

I always thought the feeling was that the ground wasn’t sufficient on an XB which wasn’t allowing the coil to create enough of a charge on the primary side, and the supplemental wire resolved that. But, after reading in the service book that it doesn’t require being attached to the chassis to work, is the wire just a placebo?
 
I did the same with the points in a 51 chevy:upset: Ya never forget that one! I couldn't even afford new ones:down: so I spent 1/2 a day un-welding them and filing them back into shape.

The ignition trigger on the primary windings IS the "ground" to collapse the coil.
49718880531_a3de192678.jpg


Terminal 1 would be the ignition hot (+) and terminal 15 would be the (-) trigger, but theres no chassis ground. It doesn't need one to operate because thats not where the 'circuit' is. The circuit completes across the plug gap.
49718880716_efbbf50493.jpg


The ground wire your talking about just goes to the outer steel sandwich plates that hold all the windings around the iron core. It's for ignition noise so it doesn't upset the ECM.
 
Ok, so we are on the same page.

That’s how I got home that night also. I replaced them the next day, but i was able to break them free fairly easily. Luckily I didn’t just sit and crank the motor until I wore the battery down. I had heard the rumor about that happening to points but Murphy’s law needed to wait until the time I needed the car to start the most. That car never left me stranded, but after that time everyone thought it was unreliable. I do not miss points!
 
Just stick a suppression diode across it. That way no need for the dangerous high voltages...

Points....When a matchbook was also in my tool box.
 
RB: Where does one even find a book of matches anymore:upset: They're dang-er-ous!

34:19 Totally right?! I'm working on the '57 right now and feeling a little torn about upgrading the ignition. Point ignition is EMP proof, so when the bombs go off I won't have a car to drive with Mad Max. LOL
 
Matchbook??? was that to file down the points? Sorry, was a little bit before my time.

Tried to google it, and ended up going down the rabbit hole with threads on Reddit for sharpening hypodermic needles for IV drug users. Yikes
 
Gapping and cleaning, that or a crisp new dollar bill also for cleaning.

I got one for you so called old farts, before synthetic oil, how many of you added one quart of auto trans fluid to the oil when changing it ?
 
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I never did that, but I had the spout you would jam the sharp end onto the top of a tin quart can of oil.

Probably illegal now... Sharp edges can KILL!:eek:

and I still own a dwell meter:tongue-new:
 
I may have one of those spouts still. Edit: I don’t anymore.


I’ve done the atf trick before on an older dirty motor. I’d let it run at idle for about 5 minutes before dumping the oil.
 
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Open the air cleaner, rev the $h!t out of it and pour tranny fluid down the carb.

Cooter, got me beat. Working on rewiring a 61 Willys, PO swapped in a 4.3 TBI th350. Swapping in a standalone efi. They basically took a 92ish S15 and swapped everything over. ECU in the glovebox wrapped in a grocery bag. :upset:

I may still have a spout like that. It was my dad's. Still have an old all metal flexible funnel. He used Marvel mystery oil in his 78 FLH....from a tin can.
I learned how to use a meter on an old analog simpson meter. I miss having to zero the scale to measure resistance.
I wont the mention the time I couldn't find the degauss button on the LCD monitor....:applause:
 
degauss button, LOL.

RB, Thats sounds so cool! I can HIGHLY recommend FITech for cheap, easy install, self-learning, throttle body FI. It's le$$ than most of the good carbs I've bought!
 

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