wiring loom question esp: horn connection/ whats what

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I looked through many threads, and couldn't find what I was looking for, so here goes......

Im in the process of making my 1972 750 100% roadworthy, and that led me to deciding to rewire the bike.

Got that harness by Wassell, and am pleased with it and easy enough to install with one exception- on the diagram it shows 2 wire coming out of loom (behind the front frame grommet ) ... but the loom itself has 3 wires at that point, all coming out of same strand of harness- a single red wire, a single purple wire, and a double red wire. Im guessing the single red, and the single purple are for the horn- but what is the double with a female spade connecter end for?

I'm perplexed and don't want to F this up- any definitive help appreciated.
 

L.A.B.

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Im guessing the single red, and the single purple are for the horn- but what is the double with a female spade connecter end for?

Yes, normally, a purple/black and a red with bullet connectors (attaches to the 06.2087 "Horn link lead").

The double red is unused as far as I'm aware, although apparently continues on to the accessory socket.
There shouldn't be any potential to mess anything up as both the single and double reds are ground wires.

 

L.A.B.

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Would the double red spade go to the rectifier?

It wouldn't be in the correct position and the rectifier red is normally included in the section with the other three (WG, GY, NU) rectifier wires.
WW19082_282_29.JPG
 

maylar

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There's also a chassis earth connection that grounds the frame (under the rectifier mounting screw?). Where does that come from?
 

L.A.B.

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There's also a chassis earth connection that grounds the frame (under the rectifier mounting screw?). Where does that come from?

That would be pre-'71 I believe (4-diode rectifier without the stud+ terminal to '74, not 850 Mk3 2-diode rectifier).
No need for both.
 
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that chart is wrong in two spots- the "warning light assimilator wires" are actually the wires to that right side accessory unit and the wires labeled as "blue lamp" are actually the warning light.

thanks LAB, that link help greatly.

but he says this in it - "I've got an update on that extra ground wire. I discovered this evening that it's actually the other end of the positive wire that goes to the accessory socket. Mystery solved :)."

but the accessory socket wires are the wires marked "warning light assimilator" on the chart. So that extra wire still doesn't seem to be in play. I don't see how in fact it could be. If that OP is around, I'd like to hear his views

So best advice hook it to the single, and just leave the double?
 
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I'm thinking sin 've the horn has a double connection and a single, that the double connection might thus be for the horn, double ground?
 

L.A.B.

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but the accessory socket wires are the wires marked "warning light assimilator" on the chart.

Yes, so the accessory socket wires are in fact a single brown/blue and single red (no terminals) and the accessory red wire is probably one of the double wire 'legs' attached to the unused red double-wire spade.
The harness ground wire doesn't match the Trust Lucas (Wassell) diagram as apart from the errors mentioned the double red isn't shown.
Note that the rear R/H and L/H indicator wires are also incorrectly marked as green/red is LH and green/white is RH.
Edit: The white/yellow ballast to coils(-) wire was white/purple originally so wrong on the diagram and in the harness.


So that extra wire still doesn't seem to be in play. I don't see how in fact it could be.
As both reds are joined at the spade terminal then there is continuity whether the spade is connected or not.

I'm thinking sin 've the horn has a double connection and a single, that the double connection might thus be for the horn, double ground?

You could connect both reds to the horn if you wanted to but as both the harness reds (single and double) should be 'common' there's probably nothing to be gained.
 
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That makes sense. So one last question- would you then just leave the double red unattached?
 

L.A.B.

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That makes sense. So one last question- would you then just leave the double red unattached?

Technically, there seems to be nothing to attach it to (unless you were to double-up the horn ground) and it's probably an Interpol (relay?) wiring connector that has been overlooked as all the unnecessary Interpol wiring has been removed from the latest harnesses.
 
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found the solution thanks to Grant Tiller.

He says: "If there is no continuity (as per the OEM factory harness), then you need to plug the single red cable with the bullet on the end into the double red cable socket.
The vacant socket on the double red cable is then used for the ‘horn link lead’ which is a short length of cable that lengthens the red and purple/black leads for the horn. The ‘sub harness’ is terminated with bullets at one end and spades at the other.""

thanks to all here- a good responding site here, and I'll
be back often I'm sure
 

L.A.B.

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found the solution thanks to Grant Tiller.

He says: "If there is no continuity (as per the OEM factory harness), then you need to plug the single red cable with the bullet on the end into the double red cable socket.
The vacant socket on the double red cable is then used for the ‘horn link lead’ which is a short length of cable that lengthens the red and purple/black leads for the horn. The ‘sub harness’ is terminated with bullets at one end and spades at the other.""

Ah, that would explain it as you said in your first post: "but what is the double with a female spade connecter end for?" so I was under the impression it was a double red with a single female spade terminal and not what I now believe to be two single reds with bullets connected to a double-common (4-way common) bullet connector (below)? Checking my own Commando didn't help as it's an 850 Mk3 which doesn't have the same three red wires, however, glad it's sorted.
prod_large
 
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I noticed on my New Wassell harness that one of the ‘spare’ red earth wires was actually not connected and I only discovered this when I tried to use it.
 
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yes my fault, first glance made it look like a spade to me, 2nd glance showed it wsan't.
 
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So wiring is done with 1 exception. From the left handlebar control comes a red/white wire that is for the kill switch. I see no other red/white wire on the main loom. Where does that kill switch wire go? Other than that the wiring is complete, and everything I can test on a non running bike works as should. Will be rebuilding carbs this morning..... unless the unexpected occurs will kick it over this afternoon. I truly appreciate the help
 

cliffa

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That is the wire from the normally unused button designed for the starter. Just tape up the end or plug it into a spare bullet connector ( Or Buy a starter kit :) )
 

maylar

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The kill switch would be a white/yellow. The white/red is from the "spare" button. On an OEM harness there would be another white/red in the big bullet socket bundle, but that wire went nowhere (taped up under the tank).
 
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