Wiring harness question

So, my 74 850 is down to the frame. The wiring harness is not good. Replacing it with a OEM one seems a little dated. I am not restoring it to

original condition and any mod that will be more reliable & safe is the goal here. All the wires on the OEM harness would not be used and the upgraded

electronics, Tri-spark, better alternator, etc. may require updated wiring. My question is that to make my own harness would it be real difficult knowing

that most components used the "Lucas bullet" and some use a more modern connection, (turn signals, CNW horn, upgraded brake switch, etc. )

The cleaner, reliable style is what I'm after. What would be your suggestion or Opinion?

Make your own, it is much cleaner. You can get super quality connector bullets from McMaster Carr or motorcycle type from many vendors on the net http://www.britishwiring.com/Comp.htm is one http://www.vintageconnections.com/ is another I always do mine because I place things in different locations, use a better handlebar control, a rectifier/regulator rather than the Lucas rectifier and zener...

Jean

Agree with Jean - make your own. Use spade connectors and make sure you have a decent (ratchet) crimper.

If you're going for custom, wouldn't it be better to solder not crimp the connectors? Also, is it desirable to eliminate those white multi-prong connectors or do we have to suffer with some interconnectors to make the harness usable?

I find these connectors very handy for things like handlebar switch leads, etc.
http://www.summitracing.com/parts/MSD-8171/

I like to keep the same color code as the original wiring diagrams to make trouble shooting easier. British Wiring can supply the wire. Use as few connectors as possible and still make the harness removable. Lucas male bullet connectors are fine, but the sleeves are crap. If you do use these make sure to use new sleeves and some dielectric grease.

If you use spades or bullets, use a good (ratchet) crimp tool rather than solder and heat shrink for strain relief. A good quality open barrel terminal with a piece of heat shrink is better than the plastic sleeve type found at auto parts stores.

Here's some good info on terminals and connectors. These can be found at Mouser or Digi-Key as well as Eastern Beaver.
http://easternbeaver.com/Main/Stuff/Faqs/DIY_Page/diy_page.html

Consider relays. Read the section on them at the Eastern Beaver site link above.

Use loom tape (not electrical tape) with heat shrink tubing at the ends

powerdoc said:

...wouldn't it be better to solder not crimp the connectors?

Click to expand...

Solder will wick up the braids of the wire and it will embrittle the connection with age and vibration. A properly executed crimp will form a cold weld and will give a secure and long-lasting connection. I also cover every connector body with heatshrink to protect against water ingress. Slows things down a bit, but adds strain relief as well.
(Maybe I should do a little write-up on wiring sometime?)

Wow! What a great response! I will make my own harness. The info here is encouraging and the task seems less daunting thanks to the responses here and with some guidance from Matt at CNW. The support here is great!

The links provided by jeandr, Ron L, and tips about crimping vs. soldering by others is very helpful stuff. I really was not looking forward to the gigantor harness made in 1974 on my custom build. I was cringing at the thought. Any and all opinions are welcome.


*Testing the resistance of a Lucas system:

Yes to doing it all yourself. As suggested at a rally tech session ,crimp then solder,with heat shrink to slip back over the connection and wires to help provide support and keep moisture out. So that is what Crazy (my Combat) got/gets for her life. Another person told us to build your electrics around the horn (not Lucas) with relay. High and low beams with separate relays too. Ground (earth for you purist types) to the frame very securely too. This winter I plan to obtain a multiple fuse block so that when failure occurs away from home I can isololate the cause to a particular circuit and minumize tracing. placed near the strong battery of course. Peter.

Another vote for doing the harness yourself. Concerning the solder-vs-crimp controversy, soldered bullets are much more corrosion-resistant than crimped, but soldering requires more skill and technique, and a bit more time. Using heatsinks below the bullets will prevent solder flow into the wire stands and thus avoids mechanically stiff joints (take a look at the bullet joints in the original loom to see what I mean). Apply a short piece of heatshrink tubing over the joint. If you don't have good soldering skills, and don't want to learn them, then a high-quality crimping tool is the next best option. Rather than loom tape, consider flexible loom tubes (black mesh) available by the foot at electronic supply shops. Sold in many diameters, this stuff allows you to add and subtract wires to and from the loom easily. Like loom tape, applying a bit of heatshrink at the ends makes for a neater job.

As an aside, this is the perfect time to think about a negative-ground conversion, and avoid all of those pesky red ground wires that will have to be replaced if you postpone this conversion. A negative-ground system allows you to fearlessly use standard battery tenders and add useful stuff like GPS and LED lighting. You'll need a modern rectifier/regulator and likely a new assimilator as well.

I am doing the wiring on a Commando at the present time, this is a picture of the battery box area



I made an aluminium plate to hold the battery in place and hold the fuse block plus the main relay. The rectifier/regulator is on the left of the battery and the horn is just in fron of the battery box. I used a relay because the switch I am using is only good for a few amps while the relay will carry full battery current.

The owner has a shortened rear loop and a shortened rear fender. I made the license plate holder from aluminium plate with a rear light from e-bay (LED of course)



This is an interesting mod, his headlight shell is completely devoid of indicators, no lights, no idiot lights, so I put the high beam indicator inside the control switch.




While there is a ground inside the switch, but I wired it like so



When on low beam, the LED does not get any power, on high beam, the LED gets +12 from the switch and the circuit is completed through the low beam filament. This indicator has two functions, it can under normal circumstances indicate when the high beam is selected and it will not light up on high beam if the low beam filament is burned out

Jean

YesYesYesYesYesYes. This winter, Incredible drive today.

In the diagram I posted, the headlight bulb is drawn as it it was a single filament bulb, that is the symbol I have in my copy of visio, just pretend it is a dual filament bulb on the diagram and if you decide to copy my modification, it will work as shown on the pictures.

Jean

Jeandr said:

While there is a ground inside the switch, but I wired it like so

When on low beam, the LED does not get any power, on high beam, the LED gets +12 from the switch and the circuit is completed through the low beam filament. This indicator has two functions, it can under normal circumstances indicate when the high beam is selected and it will not light up on high beam if the low beam filament is burned out

Jean

Click to expand...

Corrected the drawing for the indicator...

Jean