T140V 1977 negative earth? - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 10 (permalink) Old 04-17-2019, 04:27 AM Thread Starter
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T140V 1977 negative earth?

Rebuilding my Bonnie and have decided to upgrade the Lucas electronic ignition with a digital Tri-Spark recommendation. The thing is, I don’t know if my bike is negative or positive earth? Engine #EP83784. Appreciate any advice
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post #2 of 10 (permalink) Old 04-17-2019, 01:43 PM
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The fact that it was ORIGINALLY Positive earth, means almost nothing.

A previous owner could have converted it.

Simple enough to trace the main heavy lead from the battery to the frame; if it's from the positive terminal of the battery, it's positive earth. If from the negative terminal, negative earth.

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post #3 of 10 (permalink) Old 04-18-2019, 10:20 AM
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Hi,

Firstly, welcome to the Forum. I've moved your thread to the main Forum, where more regulars are likely to see it.

Quote:
Originally Posted by GoBonnie77 View Post
donít know if my bike is negative or positive earth?
Your bike would've been "positive earth" originally. However, as Paul posted, it's easy to check what it is now; as well as Paul's suggestion, if you connect a Voltmeter (or multi-meter set to Volts) between a point on the frame or engine and first one battery terminal and then the other one, one connection will cause the meter to display zero Volts, that's "earth" (the other terminal will (should) cause the meter to display around 12V).

Quote:
Originally Posted by GoBonnie77 View Post
decided to upgrade the Lucas electronic ignition with a digital Tri-Spark recommendation.
Why, unless the Lucas e.i. isn't actually working? The Lucas e.i. - known as Rita - is known to be very reliable.

Neither Rita nor the Tri-Spark e.i. care whether the electrics are "negative or positive earth". Neither e.i. "earths" through any of its components; unless the bike's been rewired very badly, its existing wiring has some wires connected to battery +ve (Red-insulated wires as standard) and some wires connected to battery -ve (as standard, insulation any colour or combo. except plain Red ); both Rita and the Tri-Spark e.i. have +ve and -ve wires; if they're connected to corresponding wires on the bike (as opposed to sundry other bits), "earth" isn't an issue.

Changing the subject entirely, please would you put at least basic machine details and a basic location in your Forum User Profile? These'll then appear beside all your posts, help respondents if the advice required is machine- and/or location-dependent.

Hth.

Regards,

Stuart
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post #4 of 10 (permalink) Old 04-18-2019, 10:27 AM
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Quote:
Originally Posted by GoBonnie77 View Post
Rebuilding my Bonnie and have decided to upgrade the Lucas electronic ignition with a digital Tri-Spark recommendation. The thing is, I don’t know if my bike is negative or positive earth? Engine #EP83784. Appreciate any advice
Hi Go Bonnie,
That’s a nice looking T140.
Your engine number denoted a build date of May 77, at this time the T140V was fitted with a positive ‘earth’ wiring system. But they were fitted with points not the Lucas Rita ignition.
The Lucas Rita became a standard fitting in 1979 and was married to a Negative ‘earth’ (sorry Stuart) system.

This means either the ignition was wired differently, or the bike was converted to accommodate it.

If the wiring loom is ‘original’ and is still Positive Earth, there should be a bunch of RED wires connected to the + terminal of the battery, and a fused brown/blue wire connected to the - terminal of the battery.

Please note the emphasis on ‘original’ there has been 42 years for previous owners to change things.

If you post a photo of the battery and connections, it is very likely that the connection type will be easily recognised.

Regards
Peg.
EDIT: I was typing at the same time as Stuarts reply and can see that he has already answered your question.

Last edited by Rancidpegwoman; 04-18-2019 at 10:30 AM.
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post #5 of 10 (permalink) Old 04-18-2019, 10:53 AM
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You may go further between breakdowns with a Rita, than a Trispark.
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post #6 of 10 (permalink) Old 04-18-2019, 12:08 PM
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You may go further between breakdowns with a Rita, than a Trispark.
Yes

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post #7 of 10 (permalink) Old 04-19-2019, 10:48 PM
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Not much further though

I can remember walking into a british bike shop [well known and patronised] in the '80's and there was a big bucket of old Rita ignitions holding the door open.

I also had one on my TSS that was faulty, its the reason I ended up buying it, the original owner knew nothing [I knew the very brief low km 'history', so it was a good buy for me]. I fitted a Boyer and never looked back.

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Last edited by tridentt150v; 04-19-2019 at 10:57 PM.
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post #8 of 10 (permalink) Old 04-20-2019, 03:52 AM
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Hi,

Quote:
Originally Posted by tridentt150v View Post
Not much further though
I can remember walking into a british bike shop [well known and patronised] in the '80's and there was a big bucket of old Rita ignitions holding the door open.
I also had one on my TSS that was faulty, its the reason I ended up buying it,
I fitted a Boyer
While, by definition, not every AB11 amplifier would've been perfect, it's long been well-known the oe '79-on 5PU pick-up was far more unreliable. Possibly exacerbated by higher ambient and engine temperatures in Oz? Before fitting the "Boyer", did you try a Mistral replacement for the standard 5PU?

"in the '80's", the Co-op having closed, Lucas having been taken over by TRW, advice and new 5PU's difficult or impossible to obtain, dealer mechanics being generally crap at electrical fault-finding and diagnosis, even many British Triumph dealers wouldn't pick up the 'phone to Mistral Engineering when the alternative was the greater financial incentive of flogging the stranded punter a whole shiny new e.i. ... Absent the internet to inform an Australian dealer that a cheap 5PU replacement even existed, I suspect replacing the whole e.i. with the only alternative probably looked like a 'no-brainer'?

Quote:
Originally Posted by tridentt150v View Post
I fitted a Boyer and never looked back.
Mmmm ... the vast majority of "Boyer" owners I came across "in the '80's" had been looking forward ... to their riding mates disappearing down the road ... Otoh, struggling to remember any stranded Rita owners ...

The reason Steve Kelly began Tri-Spark was he was a T160 owner and, at the time, "Boyer" was the only e.i. available new, "My Boyer doesn't work" letters had filled Club and national magazine 'Help' pages for years (otoh, "My Rita doesn't work" letters were very rare), and were a regular thread title on the then-new internet forums. The 'Classic Twin' e.i. problems might've tarnished Tri-Spark's reputation on this forum but, certainly over on TOL, Steve remains on course for sainthood.

One of the stated reasons Andy left Bransden Electronics to start Pazon was Ernie's persistent refusal to update particularly the Mk.3 analogue. It's noticeable that, since the Mk.3 was superseded by the Mk.4, "My Boyer doesn't work" forum threads have virtually disappeared ...

Regards,

Stuart
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post #9 of 10 (permalink) Old 04-21-2019, 10:14 PM
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No internet [or a very crude facsimile albeit a not very well used or known one] was certainly a driver for Boyer. Also the fact that talking about and then getting anything Lucas/Mistral was weeks if not months away, a Boyer was on the shelf. That plus I had one on the Trident and it worked.
Lastly, if you have a certain product and it fails...who rushes out to buy another one. No, you shop around and buy a [hopefully] more reliable alternative. Once bitten, twice shy they say.
BTW, the vast majority of twin owners were [in that day and age] reverting to points....or so the shop owner said, again probably because they were readily available on Oz.

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post #10 of 10 (permalink) Old 04-23-2019, 05:07 AM Thread Starter
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Thanks very much for all perspectives, history and advice. Very helpful and much appreciated. Have established positive earth but time off work has ended, so it’ll be some time before I can report back on results. Thanks again, great forums. LG
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