home made harness question about neg/ground

emzdogz

Aunty Em
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Am starting to figure out exactly how I will put my "simplified" harness together, after having looked at bunches of the ones shown on here.

(Thanks, btw, to those who contributed those for all to see and use)

Question: the components that show a "ground" symbol by them - can I just run a long wire along the length of the bike, which is grounded to the frame itself, and then connect all these things that need grounding into THAT wire?

Also how can I know what components ground themselves to the frame, just by the way they mount?

Am wondering about the starter motor. It is grounded by making contact to the frame through its mounting bolts?

Also the coil. Am using a Mike's black aftermarket coil on my 80 w/stock ig. Is it supposed to ground through the mounting screws? I think I'd read somewhere (that I can't find now) where the plastic around the metal inserts that the mounting bolts go through, should be ground down a bit to allow the fasteners to contact metal all the way from top of fastener through metal insert and on into mount.
But I see I had a seperate ground wire coming off the coil from "before" - when I had the bike running a few years ago with this coil.
Is either method ok?

Wondering about grounds on reg/rect and alternator....

From looking at this diagram I see these things have the ground symbol:
Tailight
starter switch
battery
alt
reg/rec
starter motor
headlight

tail light headlight and battery, no prob - I understand how to ground them - they get a pigtail to a screw on metal housing, right?

but as far as providing a ground for reg/rec, alt, starter button - can those all connect into one common long grounded wire?

thanks, sorry if this is boneheaded...

(I have been reading the various elec threads but haven't gleaned any info about this, specifically)

what I'd like to do is run about 8 long wires through the frame (a couple will be unused, I guess) and have one of them be a ground wire.
 
one large grounding wire will work, just like it does on a stock harness. it's a larger gauge than most of the wires on the bike. pretty sure coils don't need to be grounded since there's a + and - on them. (mine are not on a '78)

battery has a separate ground to frame. lights, switches, regulator, etc can be grounded to your harness and mounted to the frame somewhere.

use lock washers so the grounds don't shake loose and drain your juice.
 
you also need a large ground wire from the battery - to the frame and or engine for the starter loads.
 
emz...,

It's also important to know what parts of the bike are nor grounded to the frame. There is a tendency to think that if it's a metal part of the bike, it must be grounded, but that is not always the case. These parts are not grounded. You might actually measure continuity from them to the frame, but thats just a "casual" or accidental ground. Not a ground that you can depend on and will drive you nuts trying to trouble shoot an intermittent condition, such as a tail light that sometimes doesn't work or the horn or starter button, etc.

Not grounded to frame (and the components affected that need a separate ground wire):

1. Headlight bowl. (turn signals) Ground provided from harness.
2. Handles bars. (Horn and start button) Ground provided with black wire to horn button makes contact to bars for the start button.
3. Gas tank. (Static discharge) No ground. Should be grounded to prevent static buildup.
4. Battery box. (Rectifier, regulator) Some rectifiers provide a ground through the center mounting bolt.
5. Rear fender. (Tail and stop light) Accidental ground from incidental metal to metal contact or worn through rubber bushings. Tail light needs a seperate wire ground.
6. Carburetors. (?) Accidental ground through throttle cable from handle bars and horn button ground. Potential fire hazard if that ground is intermittent.

So, the idea of providing a continuous wire connection to the frame from one end of the bike to the other is actually better than the factory wiring!

The black coil from Mikes that should have the plastic removed from its metal core does not require a ground. The reason for removing the plastic is to provide a better path for heat dissipation, but it does end up being grounded.
 
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thanks for the info!

One more: can it hurt if something ends up grounded twice? i.e if it is grounded through its mounting bolt, but then you attach to a ground wire, too?

Pete, thanks for info re: removing plastic...

:)
 
one weird thing from long ago....
I couldn't for the life of me get my bars to ground. Tried all kinds of things. Then, connected clutch cable (it was hanging loose before) and bingo, they were grounded and it worked - fired right up.
 
emz...,

No harm done with multiple grounds to the same device. Your clutch cable experience is another example of a "casual" ground. Not something to depend on.
 
Hi Emmer.....Not a "boneheaded question in the lot". Might help to think of what you'd have if after running those "eight long wires" to everything that needed grounding, you then stripped the insulation off each wrapped & tied them all together and then insulated the assembly. That would then be a lot like your stock grounding circuit and could be thought of thereafter as one heavy duty wire to which all grounds were connected. ie the black wires in a stock XS650 harness.

Couple of suggestions: 1. Get Jayel, Pamcopete, Grizld1, The Retired Gentleman or some other certified guru to move next door or.....

Get a copy of Tracy Martins Motorcycle Electrical Systems :thumbsup:

http://www.motorbooks.com/Store/Product_Details.aspx?ProductID=36878

This book is so good, readable and understandable! Of course a good clear, colored copy of both the stock WD for your particular bike and one representing where you think you're headed will help greatly as well.

2. Get a used harness from the same/similar model bike that you have to start with...(80' SG ??) and essentially trace out that which you're sure you don't need from it while also building in everything you do.....including the grounding circuit you describe or say a headlight off/on switch??? Bringing each connecting wire to the length you desire while cleaning, repairing or replacing each connector as you go ......please solder wires to connector terminals. This will result in a harness that's still (though altered) compatible with your stock WD and both you and/or some future owner will bless you beyond measure for the consistency.

You will also have gained great insight into the electrics of your motorcycle and better yet will have made them to be just what you wished them to be also.

Hope this helps and that the guru's referenced, check in to contribute/correct and don't mind the temporary relocation suggested. btw...I believe Jayel prefers Science Diet with his beer. Best, Blue

ps....I think we're going to have to have Pete "bronzed" for posterity! Great Stuff As Usual
 
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Hi Blue, well the 8 wires were not all going to be grounds, I was just thinking one heavy gauge ground with offshoots spliced in where needed. The rest would be other wires in the diagram.
Thinking I will dissect the old wiring harness though.
And thanks much for the book recommendation - I will check it out!
:)
 
I might add that all painted parts need an unpainted spot to get a connection, I know this sounds very basic, but it can happen. Frames, engine mounts, handles bars are an example.
On my 75 the handle bars are grounded with a wire that is hooked under one of the riser nuts to one of the upper triple tree clamp bolts. It could also be hooked to the frame at an upper motor mount or coil mount.
Most stock parts that need a ground usaully ground with a black wire.
When I rewired my 75 I ran my grounds with a common wire and this common wire went to the battery.
Your starter grounds through it's mount to the engine. Because of this your engine needs a good ground. Any or all of the engine mounts should have a bare metal to bare metal connection, well some dialectric grease to prevent corrosion.The easiest mount to use is the top engine mount.
 
why to not run a ground wise direct to the battery: if, for some weird odd reason, something high draw loses it's frame connection (like your ground strap wears through), there's a good chance it will try to ground back though your wiring. Causing smoke, flames, and a lot of excitement. You can safely ground that common wire to the same point as you ground the battery to the frame.

Just sayin', from experience.
 
am revisiting this old thread of mine, since I am now finally doing the wiring. Got lights, got brake lights, got charging and ignition stuff hooked up, but haven't attempted to run bike yet.

It would be seriously tidy and convenient at this point, while I have it kind of apart, to run the wires through the frame. I already have a hole (entry point) at the back, where part of the frame (before it was cut) formed the "V". But at the front I'm wondering where the best place would be to drill a hole. I guess on the underside of the main backbone, kind of right behind the steering head?

In order to use a rubber grommet, the drilled hole would have to be kind of big....I'm wondering if this is a bad idea, for frame strength/structural integrity reasons.

If anyone else reading this has made a bike where the wiring runs through the frame, I'd love to know where your forward hole is/was.

Where I'm thinking, the hole would be right above where the coil sits.

thanks!
and thanks again for the previous comments, too from when I posted at the start of this thread.
:)
 
Personally, I find that rubber grommets require you to make tool large of a hole. While they will keep you safe from having you wires chafed I have had good luck by drilling a hole half the size that you would normally use with a rubber grommet and making sure the inside and outside edges are nice and smooth. I also double up on the heat shrink at those point just to be sure. You don't want tool large of a hole in your down tube especially if there are not gussets near by. On two of the customs I built I put the hole at a 45 degree angle at the top of the down tube but not exactly on center. The 45 degree hole goes in the same direction as your wires and prevents rubbing, also, I put the holes just in front of the gas tank. it looks super clean. I have also run throttle cables that way too, but these were for Evo motor builds. Hope this helps.
 
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Personally, I find that rubber grommets require you to make tool large of a hole.

I'm curious as to what an ideal hole size in the frame should be? I want to run my wire through my frame as well, but don't want to cause the tubing to lose integrity.
thanks
 
thanks Patches, I appreciate the input.

If I don't use a grommet, I'm thinking 3/8 in hole or thereabouts.
 
here's another question: with key on (but engine not running), would it be normal to have lower voltage on one side of coil than on the other? The side, on mine, that comes from red/white wire (from TCI box), which gets power directly by T'ing into brown wire from key switch, measures like 12-13 volts with key on, something like that. But the OTHER side, the orange wire, which also comes off TCI, (but does not tie in directly to brown power wire), only measures much lower voltage - 2 or 3 volts.

At first I was just measuring it touching to the terminal on coil, but then I measured it right where it comes off the TCI box (orange wire) and even there it also only measures the 3-4 volts.

Could it be that the engine needs to be running for that wire to power up fully?

At first I thought maybe I had a bad splice or badly crimped connector or something, but since I checked it right AT TCI, I guess I eliminated that possibility.

thanks,
Em

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That wire is the ground side of the coil power circuit, one hot one ground for every circuit. THE TCI makes and breaks the ground when the bike is running. That's how you get a spark. The voltage you are measuring is coming through the coil from the red white +12 When the bike is not running the TCI opens the ground so you don't burn up the coil.
 
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