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Wiring a 1972 650 Bonneville #454690
09/17/12 10:42 am
09/17/12 10:42 am
Joined: Apr 2010
Posts: 12
Queensland, Australia
A
AusMark 72 T120V Offline OP
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AusMark 72 T120V  Offline OP
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A
Joined: Apr 2010
Posts: 12
Queensland, Australia
Hello, because of some horrifying quotes I have decided to fit a wiring harness myself. 2 questions at this stage.
Tail Light - this has 2 wires, red and black. The wiring harness has 3, Brown and Green for the Tail Light, Brown for the Stop Light and Red for Earth. Have I got the wrong Tail Light? or does 3 go into 2.
Ignition switch - This switch has 4 seperate lugs (connections). I have wired it Brown and Blue # 1, White #2 and Brown and Green #3. There is one more lug left and I have a Red wire that I can't find a home for, so I'm assuming that it goes to the remaining lug. Is this right?
Thank you
Any help would be appreciated.

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Re: Wiring a 1972 650 Bonneville [Re: AusMark 72 T120V] #454700
09/17/12 1:40 pm
09/17/12 1:40 pm
Joined: Mar 2006
Posts: 3,655
Norfolk, UK
L.A.B. Offline
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L.A.B.  Offline
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Norfolk, UK
Originally Posted By: AusMark 72 T120V
Tail Light - this has 2 wires, red and black. The wiring harness has 3, Brown and Green for the Tail Light, Brown for the Stop Light and Red for Earth. Have I got the wrong Tail Light? or does 3 go into 2.


You need to check if the wires go to separate bulb contacts for the tail and brake light (and the lamp housing is the earth) or if one of those wires is an earth wire.


Originally Posted By: AusMark 72 T120V
Ignition switch - This switch has 4 seperate lugs (connections). I have wired it Brown and Blue # 1, White #2 and Brown and Green #3. There is one more lug left and I have a Red wire that I can't find a home for, so I'm assuming that it goes to the remaining lug. Is this right?


Probably not, as red is usually positive which is on the earth side of a positive earth electrical system (unless the polarity has been changed?) so do not connect the red to any ignition switch terminal.

Re: Wiring a 1972 650 Bonneville [Re: AusMark 72 T120V] #454756
09/18/12 12:16 am
09/18/12 12:16 am
Joined: Sep 2005
Posts: 250
Tennessee
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triumphmike Offline
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Tennessee
Sounds like you have an after market tail light. The red and black wires I would bet feed negative (if you are running a positive ground) to the tail light filament and to the brake light filament of the 1157 bulb. Ground is probably obtained via the bolted connection to the fender/frame. You can check this with a couple of jumpers and a 12V battery.

Once you know which is which, the brown wire of the harness goes to the stop lamp (brake light or brighter filament) and the brown/green wire goes to the tail light. I would feed the red wire into the tail light housing and screw it down for a good ground connection.

As for the ingnition switch, the factory switch used 3 lugs (the numbers are embossed on the back of the switch) and had 4 positions:

Lug 1 - Brown Blue wire (this is your negative side feed from the battery via the rectifier)

Lug 2 - White wire (this is the switched negative to the ignition, oil pressure switch light, etc.)

Lug 3 - Brown Green wire (this is the switched negative to the lights)

If wired correctly, the ignition swith key positions are:

Key is vertical - all off (lugs 2-3)
Key is one click clockwise - ignition only on (lugs 1-2)
Key is two clicks clockwise - ignition and lights on (lugs 1-2-3)
Key is one click counter clockwise (from the off position) - lights on for "parking lights" (lugs 1-3)

If you get a shop manual for the 1972 650's there are wiring diagrams under the electrical section. I have a 1972 TR6R and this is how my bike is wired.

Hope this helps.

Re: Wiring a 1972 650 Bonneville [Re: triumphmike] #454805
09/18/12 9:18 am
09/18/12 9:18 am
Joined: Apr 2010
Posts: 12
Queensland, Australia
A
AusMark 72 T120V Offline OP
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AusMark 72 T120V  Offline OP
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A
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Posts: 12
Queensland, Australia
Thank you

Re: Wiring a 1972 650 Bonneville [Re: L.A.B.] #454806
09/18/12 9:20 am
09/18/12 9:20 am
Joined: Apr 2010
Posts: 12
Queensland, Australia
A
AusMark 72 T120V Offline OP
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AusMark 72 T120V  Offline OP
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A
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Queensland, Australia
Thank you for that, Where would the red wire connect to?

Re: Wiring a 1972 650 Bonneville [Re: AusMark 72 T120V] #454811
09/18/12 10:53 am
09/18/12 10:53 am
Joined: Mar 2006
Posts: 3,655
Norfolk, UK
L.A.B. Offline
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L.A.B.  Offline
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Norfolk, UK
Originally Posted By: AusMark 72 T120V
Where would the red wire connect to?


Unfortunately I'm not familiar with the wiring layout on the '72 models, so I don't know if that red wire has a specific connection point or not, and the '72 wiring diagram doesn't offer any clues, so perhaps another '72 model owner will be able to answer the question.

Re: Wiring a 1972 650 Bonneville [Re: L.A.B.] #454825
09/18/12 2:07 pm
09/18/12 2:07 pm
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Bishop, Calif.
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desco Online content
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If it's like mine there is a double red wire to + battery terminal and a double red wire to the frame in about the same area.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: Wiring a 1972 650 Bonneville [Re: AusMark 72 T120V] #454863
09/18/12 7:31 pm
09/18/12 7:31 pm
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Tennessee
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triumphmike Offline
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Tennessee
If you are using a stock wiring harness and the bike is still a positive ground, the red wires are the ground wires. I would route the red wire into the tail light and screw it to a ground point. You could also attach it underneath the fender to a bolt or even not use it all as your tail light could get its ground from the bolted connections.

I re-read your initial post - do not attach any red wires to the ignition switch. On my bike there is a double red wire that is attached to the front battery carrier bolt directly under the oil-in-frame fill point. One of the two red wires comes from the positive battery terminal (positive ground) and the other continues into the wiring harness to feed the ground to other points of the bike like the tail light.

Re: Wiring a 1972 650 Bonneville [Re: AusMark 72 T120V] #454941
09/19/12 11:36 am
09/19/12 11:36 am
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Queensland, Australia
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AusMark 72 T120V Offline OP
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Queensland, Australia
Thanks to everyone for the advice, I haven't finished the wiring yet so I'll have a few more questions

Re: Wiring a 1972 650 Bonneville [Re: AusMark 72 T120V] #454957
09/19/12 1:57 pm
09/19/12 1:57 pm
Joined: Nov 2010
Posts: 2,960
Boston, Massachusetts, USA
kurt fischer Offline

#irideslow
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Boston, Massachusetts, USA
Here's a good article about grounding:
http://www.gabma.us/elec/proper_grounding.pdf

Check out all the "electrical sys" section at
http://www.gabma.us/page2.htm


Kurt
1968-70-71 Triumph TR6R Bitsa - 1969 Triumph TR6R - 1971 BSA A65L - 1973 Triumph TR5T
2005 Ducati MTS 1000S DS - 2012 Ducati Hyper 796 - 2014 Kawasaki ZX1000
Re: Wiring a 1972 650 Bonneville [Re: triumphmike] #454978
09/19/12 5:51 pm
09/19/12 5:51 pm
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Scotland
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Stuart Offline
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Hi,

Originally Posted By: triumphmike
If you are using a stock wiring harness and the bike is still a positive ground, the red wires are the ground wires. I would route the red wire into the tail light and screw it to a ground point. You could also attach it underneath the fender to a bolt or even not use it all as your tail light could get its ground from the bolted connections.

confused Afaict, that makes absolutely no sense at all ... If, in "a stock wiring harness", "the red wires are the ground wires" - which they are - why would anyone "route the red wire into the tail light and screw it to a ground point"? And what is "a ground point"? confused

In a standard '72 Triumph (or BSA) harness, the network of Red (earth/ground) cables is connected directly to battery +ve. Therefore, for any given electrical circuit, both the supply from the battery (and rectifier) to the component and the return from the component to the battery are in proper, purpose-made electrical cables. Afaict, this is simple and ime it works. So 'fraid I don't understand why anyone would complicate something simple and working by involving sundry cycle parts, which weren't intended to conduct electricity (unlike the proper, purpose-made cables) so sometimes do and sometimes don't. confused

Originally Posted By: triumphmike
or even not use it all as your tail light could get its ground from the bolted connections.

No, it won't. That's exactly why Lucas put a proper, purpose-made Red electrical cable in the harness.

Hth.

Regards,

Re: Wiring a 1972 650 Bonneville [Re: AusMark 72 T120V] #455023
09/20/12 12:21 am
09/20/12 12:21 am
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triumphmike Offline
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Tennessee
Stuart,

The 72 positive ground bikes had a separate harness just for the tail light. It has 3 wires including a ground (red wire). If you read the initial post, that is a part of his basic question. The ORIGINAL Triumph tail light bulb holder had a 3 wire connection with red being one of them.

He also states he has tail light with 2 wires, red and black (one for tail light filament and one for brake light filament). I have seen these, they are after market and they get their ground FROM THE MECHANICAL (BOLTED) CONNECTION or you have to bring a ground wire to it and connect it to the metal base of the bulb holder.

If the battery is grounded to the frame via a wire, the entire motorcycle is grounded. On the 72's the tail light holder is bolted to the tail light housing which is in turn bolted to the rear fender which is in turn bolted to the frame. If you think you must have a ground wire to the tail light to make it work you are wrong. It may not be a perfect 12.5 volts (losses across the mechanical connections) but the tail light will work.

A "ground point" is any bolt the touches the frame (or engine such as the head steady).

I purchased my 72 TR6R new in 1972 so I have owned if for 40 years. I have rebuilt and rewired it several times.

Re: Wiring a 1972 650 Bonneville [Re: triumphmike] #455346
09/22/12 2:42 am
09/22/12 2:42 am
Joined: Jun 2002
Posts: 9,872
Scotland
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Stuart Offline
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Hi Mike,

Originally Posted By: triumphmike
If you think you must have a ground wire to the tail light to make it work you are wrong.

As is virtually every vehicle maker - except British bike makers - since WW2 (some even earlier)? I'm afraid it is you who is wrong, as you would know if you'd looked at the electrics of any other vehicle in the last 40 years except your '72 T120.

1. The basic principle of vehicle electrics is that, once the electrons leave battery -ve, until they arrive back at battery +ve, a given electrical component does not 'work'.

2. As most vehicles are at least mostly made of metal, at least one half of any electrical circuit - battery to component or vice versa - must be insulated from the rest of the vehicle; ime, this is done in the aforementioned proper, purpose-made electrical cable.

3. If you connect one side of the battery to a part of a mostly-metal vehicle and, by simply bolting an electrical component somewhere else on the vehicle, you anticipate that component will 'work', all you're doing is expecting the parts of the vehicle between the component and the battery to form the other half of the component's circuit.

4. In the electrics we're talking about, electrons cannot move through the paint, powder-coat, oxide, etc. that tend to be present on motorcycle parts, so any parts that have one or more of those things on its surface cannot, by definition, form part of an electrical circuit.

5. It is pointless is to scrape the paint, powder-coat, oxide, etc. off the metal because it will simply oxidise again where it's exposed to air.

Originally Posted By: triumphmike
It may not be a perfect 12.5 volts

So, given all the above, why would you not have both sides of any vehicle electrical circuit in proper, purpose-made electrical cable? confused As did and does the aforementioned "virtually every vehicle maker - except British bike makers - since WW2 (some even earlier)"? Even Lucas on harnesses it made for British cars long before it started fitting the basic Red cables' network in bike harnesses?

Originally Posted By: triumphmike
The 72 positive ground bikes had a separate harness just for the tail light.

As do '71, '73, '74, '75, etc., etc. It isn't peculiar to '72.

In my previous post is, "In a standard '72 Triumph (or BSA) harness, the network of Red (earth/ground) cables is connected directly to battery +ve. Therefore, for any given electrical circuit, both the supply from the battery (and rectifier) to the component and the return from the component to the battery are in proper, purpose-made electrical cables". At the risk of labouring the point, those are the specifics for a '72 T120 in the context of the generalities above.

To continue to be specific - Lucas supplied the three-wire rear lamp harness, the main harness and the rear lamp; Lucas intended that the three wires in the rear lamp harness should be connected at one end to the three correspondingly-coloured wires in the rear lamp and, at the other end, to three correspondingly-coloured wires in the main harness. If you do that, both the tail lamp and brake lamp circuits are completely in "proper, purpose-made electrical cables".

Originally Posted By: triumphmike
If you read the initial post,
He also states he has tail light with 2 wires,
I have seen these,

I have too. As I knew as soon as I read the original post, and as Les explained clearly, one wire would be connected to the tail lamp filament and the other would be connected to the stop lamp filament. For the record, this is exactly how your bike's standard '72 Lucas "tail light" was before '71.

Originally Posted By: triumphmike
or you have to bring a ground wire to it and connect it to the metal base of the bulb holder.

And why would Mark not do that? confused Especially as his bike has the end of a Red "ground" wire a few inches away? In the experience of everyone who's done it, or owned a vehicle so wired, that makes for reliable tail and stop lamps, unaffected by the dampness of next winter or the one after that.

Originally Posted By: triumphmike
If the battery is grounded to the frame via a wire, the entire motorcycle is grounded.

You're wrong. Using your terminology, the only parts of the motorcycle "grounded" are those in metal-to-metal contact with the wire to the battery. As I've said, paint, powder-coat, metal oxide, yadda, yadda are not "metal-to-metal contact". Worst case, if the person who connected the wire from the battery to the frame failed to remove the paint or powder-coating at the frame contact point, not one single part of "the entire motorcycle is grounded". frown

While we're here, you are also confused about "ground". On any vehicle, whether it has a network of cables for the purpose or the maker has used other vehicle parts for one side of the electrical circuits, that's all it is - one side of the electrical circuits. What it is not is "ground".

Originally Posted By: triumphmike
I purchased my 72 TR6R new in 1972 so I have owned if for 40 years. I have rebuilt and rewired it several times.

And I've rewired probably 40 Triumphs and BSA's - never mind other makes of bikes - in the last thirty years. I've never had to rewire any bike more than once.

Hth.

Regards,


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