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Is It Positive Ground?
#802563 03/24/20 1:46 am
Joined: Jun 2016
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mrcarb Offline OP
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Does a 76 Bonneville have positive ground? It would be a good idea to know this before installing a battery.

Thank you in advance

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Re: Is It Positive Ground?
mrcarb #802572 03/24/20 3:35 am
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Yes it does.

Re: Is It Positive Ground?
mrcarb #802615 03/24/20 3:23 pm
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As stock, yes.

If not stock, you need to verify by looking at the electrical connections on the zener/solid state regulator and the LT leads on the coils....

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: Is It Positive Ground?
mrcarb #802642 03/24/20 5:39 pm
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I’ve got a 77 and took the battery out after last ride in the summer n then forgot which it was. So to cure me of this old timers again I wrapped the positive leads with red tape and wrapped the negative leads with black tape. Now I always know! Gene

Re: Is It Positive Ground?
mrcarb #802825 03/26/20 3:05 am
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Like jubee says, you better check. I've changed a lot of them so I could use LEDs.

Re: Is It Positive Ground?
mrcarb #802840 03/26/20 6:32 am
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I have bikes wired both ways. I print out labels to stick under the seats in case I get senile. crazy


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: Is It Positive Ground?
mrcarb #803084 03/27/20 9:22 pm
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i also have them both ways. usually i can follow the ground wire to see what i did.


every day you do not take a chance is a day of your life that you will never get back.
Re: Is It Positive Ground?
mrcarb #803088 03/27/20 10:25 pm
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Make the determination your your bike (in case its been modified from OEM) and then buy the appropriate Triumph decal and apply it under your seat on the frame where it would have been from the factory.

Re: Is It Positive Ground?
mrcarb #803099 03/27/20 11:18 pm
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As previously stated your bike would have originally been positive ground.

If you don't know the history of the bike, it is always possible that it has been changed.

Triumphs changed to negative ground in ~1979 (allegedly because of Zener semiconductor supplies at the time). They also soon went to a completely different triple Zener setup.
I believe the single negative ground Zener was used for only a short time.
LAB may be the one to illuminate?

Your system either has a Zener or a reg/rec. Either should inform you of the polarity of the system.

Irrespective, use a 12V bulb in place of the fuse when you connect, to be on the safe side.
This allows you to be wrong without serious damage resulting.

Re: Is It Positive Ground?
koan58 #803103 03/27/20 11:43 pm
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Originally Posted by koan58
As previously stated your bike would have originally been positive ground.

If you don't know the history of the bike, it is always possible that it has been changed.

Triumphs changed to negative ground in ~1979 (allegedly because of Zener semiconductor supplies at the time). They also soon went to a completely different triple Zener setup.
I believe the single negative ground Zener was used for only a short time.
LAB may be the one to illuminate?

Your system either has a Zener or a reg/rec. Either should inform you of the polarity of the system.

Irrespective, use a 12V bulb in place of the fuse when you connect, to be on the safe side.
This allows you to be wrong without serious damage resulting.

My 79 T140D which appeared to have unaltered chassis wiring, is negative ground, three phase alternator and a single zener diode..


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Is It Positive Ground?
Hillbilly bike #803106 03/27/20 11:54 pm
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Originally Posted by Hillbilly bike
Originally Posted by koan58
As previously stated your bike would have originally been positive ground.

If you don't know the history of the bike, it is always possible that it has been changed.

Triumphs changed to negative ground in ~1979 (allegedly because of Zener semiconductor supplies at the time). They also soon went to a completely different triple Zener setup.
I believe the single negative ground Zener was used for only a short time.
LAB may be the one to illuminate?

Your system either has a Zener or a reg/rec. Either should inform you of the polarity of the system.

Irrespective, use a 12V bulb in place of the fuse when you connect, to be on the safe side.
This allows you to be wrong without serious damage resulting.

My 79 T140D which appeared to have unaltered chassis wiring, is negative ground, three phase alternator and a single zener diode..

did the bike have a single phase , or 3 phase alternator ?
My memory isn't what it used to be .
I thought by 79 it was all 3 phase , but maybe it was an option ?

Re: Is It Positive Ground?
koan58 #803107 03/27/20 11:56 pm
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Originally Posted by koan58
I believe the single negative ground Zener was used for only a short time.
LAB may be the one to illuminate?

Yes, (Lucas 49589) on the kickstart models from the '79 model year.
https://www.classicbikepartscheshir...140-norton-commando-lucas-pt-lu49589-p98

(NOT Norton Mk3 Commando!!!)

Re: Is It Positive Ground?
mrcarb #803113 03/28/20 12:40 am
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Yes Quinten, it was a 3-phase alternator in 1979, but the low output version that could still use the single Zener. Naff to cope with naff, is one way of putting it, but to cope with the high power RM24 needed either expensive matched Zeners or a reg/rec that wasn't yet avaialble.

Re: Is It Positive Ground?
mrcarb #803129 03/28/20 5:24 am
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Hi, Didn't Triumph change to negative ground when they went to Rita electronic ignition?
Don


1973 Tiger 750
Re: Is It Positive Ground?
koan58 #803132 03/28/20 5:47 am
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that makes sense , I keep forgetting about the lower output 3 phase stator .

but i dont think the zeners need to match if you use
3 zeners on the ac side as per the later/last T140's


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