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#749630 09/18/18 1:38 pm
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Good morning all. I am in the process of a frame up on a 1971 T120RV. I purchased a new wiring harness to replace my old chopped up one. The schematic page in my service Manual is not crisp at all making it impossible to understand the color codes. I am keeping + earth but switching to electronic ignition and regulator/rectifier. If anyone has any simplified diagrams or just a good color guide I would be most appreciative. I will add some photos of my beautiful project when I upload some to my computer from my phone. Any good words on proper routing of the harness along frame and between or over tubes also appreciated. as stated earlier the original loom was not in good order and I would like my routing to be as if it just rolled off the line.

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This is the '71/'72 A65 wiring which should be the same:
[Linked Image]

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Thank You so much,
The folks at CBS suggested I join and they were right.
This is perfect and legible.

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https://gabma.us/tech-articles/
Put this into your favorites. Scroll down to Proper Grounding. With any electronics you should have a ground to battery. And the headlight, taillight and engine.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
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Try this site...you can download the whole Manual free.
http://www.classicbike.biz/Triumph/Repair/Repair.htm

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Hi George,

Firstly, welcome to the Forum. smile

Originally Posted by George Henstorf
1971 T120RV.
new wiring harness
keeping + earth but switching to electronic ignition and regulator/rectifier.

You don't say which electronic ignition or regulator/rectifier you intend to use. If you haven't chosen, some general thoughts:-

Regulator/rectifier
Choose one with specific DC+ (Red) and DC- (usually Black) wires.

Although the standard alternator on your bike is 'single phase' (2 wires, as standard White/Green and Green/Yellow), consider a 3-phase (3 AC input (usually Yellow) wires) reg./rec. Reasons I suggest this are: the standard alternator on your bike is feeble by today's standards and, when you ride your bike, you might decide you want to upgrade it; for the time being, a single-phase alternator can be connected to a 3-phase reg./rec. without any problem but, later on, a 3-phase alternator could not be connected to any single-phase reg./rec. you buy now.

Of the reg./rec. available today, I advise:-

. either 3-phase Podtronics;

. or https://www.ebay.com/itm/12V-Voltag...250C-750-1000F-VTR-250-1000/382370502356 plus https://www.ebay.com/itm/Fits-For-H...or-Rectifier-Motorcycle-New/202432712013.

Any reg./rec., I always connect the DC wires directly to the battery terminals (of the above, Red is DC+, Pod Black or Honda Green is DC-).

In the harness Brown/Blue wire (wiring diagram "NU") between battery -ve and ignition switch terminal #1 are female blade terminals for the rectifier and Zener diode; these will need to be insulated securely.

Electronic ignition
If you haven't chosen already, I'm guessing you'll choose from Boyer-Bransden, Pazon, Tri-Spark 'Classic Twin' or Wassell/Vape; advantages and potential disadvantages to all.

If you haven't chosen ignition coils already, I recommend two separate '6V' coils similar to the original '12V' ... because you specifically mentioned originality in your first post and your bike has the standard mountings for them. Be aware that the '71 mounting allowed the bottom corners of some coils to contact another part of the bike when it was ... errr ... vibrating wink ... damaging the coil case; frown later oif coil mountings angled the bottoms of the coils towards the sidepanels.

Unless you already have some familiarity with BritBike electrics, none of the fitting instructions are particularly well-written, nor the wiring diagrams particularly well-drawn:-

. in the case of B-B, Pazon and Wassell/Vape:-

.. their White wire should be connected to one of the White/Yellow (wiring diagram WY) wires connected to the ignition coils (wiring diagram #19); the other end of the White/Yellow wires is connected to the 'engine kill' push-button in the switch cluster on the right-hand handlebar;

.. if you use the harness Black/White and Black/Yellow (wiring diagram "BW" and "BY" respectively), you must remove the same-colours wires to the condensers (wiring diagram #21) or insulate the female blade terminals securely;

. in the case of Tri-Spark:-

.. its Black/Yellow wire (not the BY wire in the harness) should be connected to one of the White/Yellow wires in the posted wiring diagram;

.. the harness Black/White and Black/Yellow wires aren't used;

. in all cases:-

.. the female blade terminal on the other, unused, harness White/Yellow wire must be insulated securely;

.. I never connect any e.i. Red wire just to some sundry bit of bike; like "desco", I extend it to the battery +ve terminal;

.. I never connect the coils' series ground - the Red wire from the "+" terminal of what the fitting/installation instructions label "Coil 1" - to the frame or other sundry bit of bike; I always connect it either directly to battery +ve or to the existing harness Red wires network.

Originally Posted by desco
Proper Grounding.
the headlight, taillight and engine.

Not shown in any wiring diagram is the network of Red wires that were in any original Lucas harness, should be in any reasonable-quality new harness and, as a general rule-of-thumb, provide the proper grounding for almost all electrical components:-

. Headlight - The original standard BPF (British Pre Focus) reflector/bulb bayonet cap should have a loop to take a standard bullet terminal on the end of a harness Red wire. If you bike's doesn't have the loop, be aware that the BPF bulb/lens/reflector is truly dire and you might want to consider a lens/reflector that takes a more-modern bulb with a standard H4 (3-blade) plug (which can be had to attach to a standard harness's bullet terminals). But you have to be careful which more-modern lens reflector you pick because many don't fit the '71 'flatback' headlamp shell ... facepalm

. Taillight - Lucas seem to have started fitting them with a Red ground wire (in addition to standard Brown and Brown/Green wires (wiring diagram "N" and "NG" respectively)) from about mid-'71. If you're bike's doesn't have one, I either thread a Red wire into the unit beside the other wires, attaching the Red wire to the bulb holder, or attach it with a ring terminal to one of the mounting studs.

. Turn signals - The ground path is through the chrome over the plastic bodies, so not only does that have to be in good condition but corrosion and dirt that collect in the joints between bulb holder and body and body and stem affect the grounding. facepalm Thereafter, that front turn signals screw into the headlamp shell is a good ground path, as long as the threads are clean and there's a Red wire from the harness attached to the shell; but the rear stems screwed into a painted tail-lamp mounting, that's mounted on a painted(?) fender, would be laughable if Triumph and BSA hadn't actually sold 'em like that ... shocked It's sometimes possible to squeeze another wire down the stem (it can be bare as it's a ground wire, but try not to poke it into the other wire's insulation ... whistle ) - if I can, I solder it to a washer inside the bulb holder under the spring - or you might find it simpler to attach the ground wire to a ring terminal that fits over the stem and trap it between the stem securing nut and the tail-lamp mounting.

Finally here, I've already mentioned a number of mods. that must or should be made to any off-the-shelf harness to accommodate just electronic ignition and a regulator/rectifier. However, the original harnesses were built down to a (very low) price, most pattern harnesses mimic the shag-awful original specs., which can be improved with a few other cheap mods.; would you like me to post details?

Otoh ... modern wire in original colours is available, terminals and insulators that look like the originals are available, coverings that look like the originals are available; even buying the terminal crimping tools, the total shouldn't exceed the cost of an off-the-shelf harness; if you can build an engine that doesn't blow up, you should be able to build a harness that doesn't melt. I'm not sure about my ability to build engines that wouldn't blow up but I haven't had anything to do with an off-the-shelf harness in about thirty years. smile

Hth.

Regards,

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1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
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I recently designed and built a +ve earth harness for my 59 5Ta. The PO had made a number of upgrades inc 12V conversion, EI, and later style handlebar switches. I know very little about about electrics, so with Stuarts advice I designed a loom which was quality assured by Stuart. I also eliminated the zener and wired in a reg/rec

Once that was done I bought all wires, terminals etc from Vehicle Wiring Products in the UK. Looking at my order history with VWP, the cost came to around £85, but I borrowed a Delphi crimping tool from a pal. I overestimated some wiring colours and underestimated some others (mainly red wire and white wire) so I needed to dip back in at an extra cost of £3.95 shipping each time I reordered, so make sure you do your sums as I could have knocked just short of £12 off my final bill.

I also used the 6.3mm uninsulated jap connectors, for which I also bought the correct insulating sheaths instead of the Lucas bullets for no reason other than I had access to the crimping tool, but even with my very limited experience in this field, I found them very easy to crimp and as each terminal is insulated, I have no fear of a dead short should the male and female work loose.

Anyway, it was an experience I initially dreaded, but once I got my head around what I was doing, I thoroughly enjoyed it

















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I have used a Tympanium rectifier/regulator for my single phase generator for years without problems. Regulators have to be heat sinked. They regulate by shorting the excess current.

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Originally Posted by DMadigan
I have used a Tympanium rectifier/regulator for my single phase generator for years without problems. Regulators have to be heat sinked. They regulate by shorting the excess current.


Most modern rec/regs dont short excess dc current .
The regulation is on the ac side .

They regulate by shunting the ac induction from the stator .
Meaning any extra magnetic potential is left in the stator
And only enough ac is allowed to exit the stator
to support a set dc battery voltage .
There is a certain amount of conservation of energy to this method.
With the loss being only regulator switching loss .( this is the heat in the rec/reg )

Induction shunting is a completely different regulation approach than a zener shorting to ground .

The switching transistors in the regulator circut cycle with the ac wave
Which could be from 40hz. at idle , to 400hz. at high rpms .
It's this switching in the regulator
And the efficiency of the chosen semiconductors
That burns a little power as they shunt the potential ac wave .
This is not intentional heat loss
Depending on the quality of the components ,
Just unavoidable switching loss

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I converted my 1971 Bonneville to Negative Ground and used LED's for all lamps except the Headlight. This includes changing the Turn Signal Flasher to work with the low current draw of LED's and replacing the Zener Diode with one for a Negative Ground system. The 200 Watt Stator can now keep up with the bike's electrical requirements without a problem. Part Numbers and Sources for these are show where applicable.
[Linked Image]

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Few modern regulators use Zener diodes because of the heat generated by dropping the voltage across the device. Same reason for not using a transistor. Heating is a minimum when the device is full on. A Shindengen regulator uses SCRs to short the generator output across the three generator wires when the load voltage gets too high. SCRs still produce heat which is why they are packaged in a large heat sink. If the case is not attached to another heat sink the regulator output is de-rated.
I am not sure but I think the Lucas three phase regulator used three back to back Zener diodes across the three generator wires. No controller needed as in the SH640 but still suffered from the heat generated by dropping the voltage across the device.
Modern bikes use LEDs to reduce the power required. The generator is actually smaller than they were years ago.
[Linked Image]
Of course, Lucas generators were marginal so they were not passing current most of the time which helped keep the regulators from failing.
And there is no conservation of energy. The excess is still wasted as heat, just more in the generator coils.


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