The black wire

[mew905]

I don't have a volt meter (And no idea how to work one), so I'll ask here.

Is the black wire always ground? or is it alternating? This always kind of confused me as the coils would obviously be A/C, and it seems confusing that the black wire would be DC, though I have no idea how the CDI works (if it works purely on pulses from the blue wire or what, but that would make sense as to why you have to match the black to black and blue to blue).

The reason I'm wondering is because I want to wire up an electrical system and the frame is a great grounding point in a car, but I'm unsure if the bike frame would be. It could explain why my batteries keep puffing up and I experience oddities with my lights (flickering, turning on by themselves, the tail lights dim the front light significantly, despite being on 18v (2 9v in series) to the point where on its own, it's nice and bright, but with the tail lights, I barely see a point in the road where the light is aiming (not good enough to ride with in pitch black, but cars can see me, which is the law, so it's legal here).

 

[TakeiT]

black on a multimeter is negitive, however, if its a digital multimeter it doesnt matter as much, itll show a little - beside the number if its backwards, to show negitive current


Sorry for spelling, it's late.

 

[GearNut]

The black wire coming from the mag is a ground wire. It goes to a ring terminal that is captured under the head of one of the screws that attaches the mag to the side of the engine.
Do not use this wire as a ground for anything else but the ignition system.
You can easily use the bicycle's frame as a grounding conductor for any lights or other accessories on the bike so long as all of the wire attachments points are clean and free of any paint , oil or grease, ect. (dielectric grease is acceptable though as it helps prevent future corrosion)

I personally never, ever rely on the frame as a ground conductor though. A copper wire does a much better job of conducting electricity than steel. I found emperically that running specific ground wires from each powered accessory to the negative terminal of the battery or charging system provides a much more reliable ground and even provides brighter lights.

 

[mew905]

The black wire coming from the mag is a ground wire. It goes to a ring terminal that is captured under the head of one of the screws that attaches the mag to the side of the engine.
Do not use this wire as a ground for anything else but the ignition system.
You can easily use the bicycle's frame as a grounding conductor for any lights or other accessories on the bike so long as all of the wire attachments points are clean and free of any paint , oil or grease, ect. (dielectric grease is acceptable though as it helps prevent future corrosion)

I personally never, ever rely on the frame as a ground conductor though. A copper wire does a much better job of conducting electricity than steel. I found emperically that running specific ground wires from each powered accessory to the negative terminal of the battery or charging system provides a much more reliable ground and even provides brighter lights.

So what you're telling me is that even though the engine ground is electrically "attached" to the bike frame, not to use it for lights/battery ground? But it is a consistent ground, yes? If you meant don't attach anything to the black wire, I never planned to, just the electrical ground runs through the engine into the frame and I didn't want to short it out. The clearance light I use as a tail light uses the frame as a grounding point (it runs through the mounting point so in order to mount it, I HAVE to ground it to the frame, though I DO run a second wire on a ring terminal from the grounded mounting bolt to the battery -). Both 9v batteries tend to puff up and the lighting has some oddities, which is why I needed to know if the black wire was sending AC current through the frame, rather than being a constant ground, because that ring terminal goes straight to the battery - and if it's AC, it would explain why my batteries are puffing up and getting hot; electrical short. Other than the clearance light's frame mount, the lights themselves are 100% isolated from the frame.

If anyone has a volt meter to confirm with, that would be a great help.

 

[bairdco]

the flickering and charge loss is due to the EMF radiation coming from the motor. even a regular battery powered bicycle light will flicker due to the pulses of the engine.

it's weird, but happens. i ran modified lights using cheap flashlights from harbor freight, and they'd flicker , dim, and intensify with the rpm of the engine, and the aaa batteries would die a lot faster.

if you're grounding your lights, find a spot on the frame, like the kickstand bolt, or a hole for the chaingaurd, scrape off the paint and bolt the wire on.

 

[mew905]

the flickering and charge loss is due to the EMF radiation coming from the motor. even a regular battery powered bicycle light will flicker due to the pulses of the engine.

it's weird, but happens. i ran modified lights using cheap flashlights from harbor freight, and they'd flicker , dim, and intensify with the rpm of the engine, and the aaa batteries would die a lot faster.

if you're grounding your lights, find a spot on the frame, like the kickstand bolt, or a hole for the chaingaurd, scrape off the paint and bolt the wire on.

alright, and it doesn't matter if the engine is electrically isolated? Because my green (soon-to-be) race bike has some old tire tubes between the motor and the frame (not for vibrations, its because the tubes are small and the engine had trouble gripping them) and the lights have no issues at all. Perhaps my switch is the culprit, I'll have to see when the new (proper) bike switches get here.

A side note: does anyone know where to get cheap LED turn signals? I was thinking about using the amber LED strips at walmart, but it'd cost me $70 to do one bike.

 

[GearNut]

No, it does not matter if the engine is electrically isolated. EMF stands for Electro Magnetic Field.
It is magnetic field radiation that radiates out from the whole ignition system, primarily from the mag coil and high voltage ignition coil inside the CDI box.
Using resistor core spark plug wires and resistor spark plugs greatly reduces this effect, but will not totally get rid of it.

As for LED turn signals, do a search for them on amazon. They are cheap and plentiful there.

 

[mew905]

yeah, I know what an EM field is. I just didn't think it'd do anything to my lights being that all the electrical wiring is at the closest 3" away, though the high voltage of the spark plug could possibly affect that. I'm pretty sure my wiring is the culprit for the oddities, as each individual light is super bright up until I wire up both onto the same line. I figured it may be electrical resistance in the wires as they're only 16ga, on 2x 9v batteries in series for 18v, but even in parallel they have the exact same problem: bright when a single light is used, dim when both are. I've tried running the headlight first, THEN the tail light, and vice-versa (hoping the diode function of the LED's wasn't reducing voltage too much) and both lights still dim. I'll try total frame grounding to see if that solves the issue, as right now it's only grounded to the rack, and there's a ring connector with a ground wire running all the way to the battery -, so they're both isolated and frame grounded, that and it'll look cleaner with only 1 wire running the length of the bike, rather than two. I'll also sand paint off any areas where an electrical connection is possible and used (light mounting points, rack mounting points, etc.) to ensure the grounding path is clear.

Though it seems that the 9v batteries can complete the circuit for the front light only if the body of the battery is touching metal, or the battery falls onto its side and the - touches the mounting bolt. Is the casing of a 9v battery also a ground? if so, that could explain my issues as well.