Mystery Wire II

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crusadersports said:
So (assuming positive earth) the main earth is the red cable running from the positive terminal to the crankcase stud behind the barrel. You're saying a secondary earth wire from the positive terminal (as depicted on the factory wiring diagram) is bad?
Click to expand...

Correct.


crusadersports said:
Ok, so as I don't have this bad secondary earth wire, does this mean an earth wire to the head steady is therefore a good idea?
Click to expand...

Yes, as the return current from the bike's electrical system needs a good connection from the harness to the engine in order for the return current to reach the battery through the heavy starter cable, which is, as you said, attached to the crankcase.

crusadersports said:
If the frame is isolated from the circuit because of the isolastics, I don't see the point in an earth wire to the head steady
Click to expand...

Not "frame" but "return". As there is only one wire connection to the positive battery terminal (the heavy positive starter wire) then all electrical circuits must return from the harness to the engine (head steady wire) in order to reach the battery (through the heavy positive starter wire).

For christulin:
Mystery Wire II


Note that the NVT Service Bulletin above refers to a "cylinder head lead". On early T160s, the heavy gauge positive (return) wire was connected to the cylinder head and this should not be mistaken for the harness to cylinder head return wire (which T160s also have).
On later T160s the heavy positive return wire was relocated to the crankcase.
 
Old Bloke said:
1. The wire marked R going to the "Engine Earth(Starter)", Is the thick cable designed to return the current flowing through Starter motor possibly 100amps to earth(the battery +ve in the Command).
Click to expand...

Yes.


Old Bloke said:
2. The wire marked R which Lab has marked with a big red X is an earth connection, probably to the head steady, this would be a normal wire in your harness designed to take maybe 20 amps.

3. This is the wire that Lab said should not be fitted to the headsteady as it was a mistake in the diagrams because...
Click to expand...

No, not quite. The problem is when the harness return wiring (Red) has been connected directly to the battery positive terminal, as shown on the 850 Mk.III wiring diagram.



Old Bloke said:
..if the thick cable breaks, or gets disconnected, then the current through the starter motor will return to the battery through the normal wire, and as this wire can only take @20amps, running 100amps through it will likely fry the wire right through your wiring harness. Messy.
Click to expand...

Yes-but not because of:

Old Bloke said:
So I think what Lab is saying is that Mk3 with the starter motor should not have the secondary earth to the headsteady.
Click to expand...


What I'm saying is that there should be no secondary positive wire connection to the battery, hopefully, the T160 Service Bulletin makes this absolutely clear.
 
Thanks, LAB.
Took me a couple of looks to get it. 850E wiring diagram for the starter motor is similar for earth connections to battery by way of cases, same principle. Loose or corroded connection of the heavy cable=trouble. Earth connection of wiring harness to head/cases=trouble.
 
christulin said:
Earth connection of wiring harness to head/cases=trouble.
Click to expand...

No.

A secondary earth/ground/return harness connection to the battery (+) is trouble.

If the secondary earth/return (harness red wire terminal) is disconnected (look again at the T160 Service Bulletin) then the starter motor current has no alternative route to the battery.
 
I still don't understand. Please answer a couple of questions.
The harness ground is confusing. Where is the harness grounded? Where does the headsteady wire go to? One end to the headsteady, where is the other end attached to ground?
And if the large wire is the only wire attached to the battery positive, then if this wire is broken or disconnected nothing will work including the starter?
This should be an alert that something is wrong.

Jaydee
 
jaydee75 said:
The harness ground is confusing. Where is the harness grounded?

Where does the headsteady wire go to? One end to the headsteady, where is the other end attached to ground?
Click to expand...

The headsteady wire is a small part of the harness earth/ground/return positive (red) wiring, this return wiring runs through the harness from the headlamp shell connection point to the tail lamp connections with various grounding points (headlamp shell, battery compartment/solenoid, etc.) and also connects to various items such as the 2MC and assimilator. Some electrical items initially ground to the frame (blinkers) but ultimately all electrical circuits are routed through red positive harness wiring.

To complete the circuit for all electrical systems (lights etc.) the ground/return must have an electrical pathway to the engine (through headsteady wire due to the Isolastics) as the only ground path back to battery positive is through the heavy positive wire connected to the crankcase.


jaydee75 said:
And if the large wire is the only wire attached to the battery positive, then if this wire is broken or disconnected nothing will work including the starter?
Click to expand...

Precisely, and this is generally how "electric start" vehicles are wired = one heavy gauge ground wire.

jaydee75 said:
This should be an alert that something is wrong.
Click to expand...

Yes.

If a secondary light gauge harness ground wire connected to the battery, then everything would work normally until such time the electric starter was operated and then the harness ground to the battery would either burn out or the harness/bike could catch fire.
 
L.A.B. said:
crusadersports said:
So (assuming positive earth) the main earth is the red cable running from the positive terminal to the crankcase stud behind the barrel. You're saying a secondary earth wire from the positive terminal (as depicted on the factory wiring diagram) is bad?
Click to expand...

Correct.


crusadersports said:
Ok, so as I don't have this bad secondary earth wire, does this mean an earth wire to the head steady is therefore a good idea?
Click to expand...

Yes, as the return current from the bike's electrical system needs a good connection from the harness to the engine in order for the return current to reach the battery through the heavy starter cable, which is, as you said, attached to the crankcase.

crusadersports said:
If the frame is isolated from the circuit because of the isolastics, I don't see the point in an earth wire to the head steady
Click to expand...

Not "frame" but "return". As there is only one wire connection to the positive battery terminal (the heavy positive starter wire) then all electrical circuits must return from the harness to the engine (head steady wire) in order to reach the battery (through the heavy positive starter wire).

For christulin:
Mystery Wire II


Note that the NVT Service Bulletin above refers to a "cylinder head lead". On early T160s, the heavy gauge positive (return) wire was connected to the cylinder head and this should not be mistaken for the harness to cylinder head return wire (which T160s also have).
On later T160s the heavy positive return wire was relocated to the crankcase.
Click to expand...

Aah. I think I'm nearly there: the head steady earth wire serves to complete the circuit from the loom/harness to the engine, then back along the red cable to the positive earth terminal of the battery.

This prompts the question: What happens if there is no earth wire from harness to head steady and if it is a good idea, why isn't one shown on the wiring diagram?

Thank you yet again LAB ! :mrgreen:
 
L.A.B.
I think I am in agreement with you about how this applies to Norton 850E's.
I must have a later T160, since it has only the heavy wire to the battery; I had not seen the service bulletin, though. I can only guess at the depth of your knowledge. My T160 only had 800 miles on it when I found it and was so original it may have had the original English air in the tires. Although I put a new battery in it I have an original Lucas battery for it that had never been filled.
Mystery Wire II

I hope the picture shows the clever little balls to help determine the level of the battery acid, even if they seem stuck.
 
So LAB:

1. I'm just fitting a new Sparx 3 phase regulator rectifier. This has a connection going to earth. It sounds like I should NOT connect this to the positive battery terminal, but wire it into the loom, to earth it through the head steady (and onto battery through the engine and heavy red cable). Have I got this right, that the only earth connection at the positive terminal should be the heavy red earth cable running to the crankcase?

2. So what happens if there is no earth wire from harness to head steady? If it is a good idea, why isn't one shown on the wiring diagram?

Thank You :mrgreen:
 
crusadersports said:
1. I'm just fitting a new Sparx 3 phase regulator rectifier. This has a connection going to earth. It sounds like I should NOT connect this to the positive battery terminal, but wire it into the loom, to earth it through the head steady (and onto battery through the engine and heavy red cable). Have I got this right, that the only earth connection at the positive terminal should be the heavy red earth cable running to the crankcase?
Click to expand...

There's no pathway for the electric starter current through the Sparx reg/rec, so it doesn't matter if the Sparx Reg/Rec positive wire is connected directly to the battery(+).



crusadersports said:
2. So what happens if there is no earth wire from harness to head steady?
Click to expand...

Due to the Isolastics, if there is no direct wire connection between the harness return wiring and engine then the electrical system will have to find an alternative pathway to the engine (through the control cables etc.) in order to function.
What you appear to have overlooked is that with only the heavy gauge positive wire connected to battery(+) then the only way the MkIII electrical systems can complete the circuit to the battery(+) is through the heavy gauge (engine - battery) positive wire attached to the crankcase, therefore the return pathway for the MkIII electrical system must go to the engine in order to reach the heavy gauge positive wire fixed to the crankcase, and then through it to the battery(+).


crusadersports said:
If it is a good idea, why isn't one shown on the wiring diagram?
Click to expand...

The wiring diagram is a schematic drawing, and not intended to be an absolutely accurate representation of the actual wiring harness.

850 MkIII manual does say this:

Section F1.24
"Remove the main engine steady plate by taking out the three socket screws and washers, releasing the suspensory spring device as in C 'O'. Note that the centre screw secures the ground (earth) lead tag."
Click to expand...

Section F3.13
"Fit the main head steady plate to the cylinder head, securing with the three socket screws. Note that the centre screw secures the ground (earth) tab on the red leads."
Click to expand...

Period photos show the wire terminal in a different location, between the rear spacer and side plate.
Mystery Wire II
 
There's no pathway for the electric starter current through the Sparx reg/rec, so it doesn't matter if the Sparx Reg/Rec positive wire is connected directly to the battery(+).

Ok - that's great- thanks

Due to the Isolastics, if there is no direct wire connection between the harness return wiring and engine then the electrical system will have to find an alternative pathway to the engine (through the control cables etc.) in order to function.

So the electrical system would function and the bike run, but with marginal efficiency. Recipe for a poor earth = dim lights, misfiring, etc?

What you appear to have overlooked is that with only the heavy gauge positive wire connected to battery(+) then the only way the MkIII electrical systems can complete the circuit to the battery(+) is through the heavy gauge (engine - battery) positive wire attached to the crankcase, therefore the return pathway for the MkIII electrical system must go to the engine in order to reach the heavy gauge positive wire fixed to the crankcase, and then through it to the battery(+).

No I think I've got that thanks: as you said earlier: harness, engine, cable, battery.

So if a secondary earth wire from the positive terminal of the battery is a bad idea, primarily because it can't do the work of the heavy red cable, would it be ok to have secondary earth wire if it was also a heavy gauge cable like the main red cable? I have the CNW starter motor cable upgrade set which contains four cables:

Long red= main earth cable from positive battery terminal to crankcase bolt
Short black= solenoid to battery negative terminal
Long black= solenoid to starter motor

When I asked what the fourth (short red) cable was for, I was told it was to go from the positive terminal to the frame to set up an earth return for things like the indicators, etc. Reviewing all that we've said about a secondary earth being a bad idea, I'm wondering if this would be ok as it's the same gauge as the main red earth cable?

Continued thanks for your help with this LAB :mrgreen:
 
If I understand correctlly, connect red/ground wires to a convenient head steady bold that is isolated from the engine by rubber. I use this area as a convenient location to connect extra ground wires from lighting, ignition, etc. so you don't have to depend on the frame for good grounding. When I have built wiring harnesses, I use larger guage wires for ground or other circuits that carry a lot of current. I think it is a good idea to have separate fuses for ignition, for headlight and indicator lights. A blown fuse gives you a direction to look for a short and leaves the other systems operable.
 
The engine needs an earth path back to battery just for the spark plug gap current to flow for lots of instants in a row, so does not take much copper or other paths to conduct that brief high voltage but certainly could suck down the spark intensity w/o a nice wire way. I used the upper rear fender bolt as my main Earth termination for relays and dodads so there was only one red lead to the battery. A screwed down to the lamp shell earth terminal instead of blade or bullet connector solved a good bit of my prior fault finding. Feel the bar switch temp for headlamp sense of path draw down. Connections always the weak link and resistance points so I'm pondering a low low temp [hair drier level] solder to make and break connections on my terms, expect screwed down ones like the battery. At least a 1/4 hp freed up by removing the police copper wiring mass and about 1/3 less clutter and 150% easier tracing faults.
 
crusadersports said:
So if a secondary earth wire from the positive terminal of the battery is a bad idea, primarily because it can't do the work of the heavy red cable, would it be ok to have secondary earth wire if it was also a heavy gauge cable like the main red cable?

Long red= main earth cable from positive battery terminal to crankcase bolt
Short black= solenoid to battery negative terminal
Long black= solenoid to starter motor


When I asked what the fourth (short red) cable was for, I was told it was to go from the positive terminal to the frame to set up an earth return for things like the indicators, etc. Reviewing all that we've said about a secondary earth being a bad idea, I'm wondering if this would be ok as it's the same gauge as the main red earth cable?
Click to expand...



Not a good idea (and still basically unnecessary in my opinion). Personally I think CNW has got it wrong if they supply a secondary light gauge cable as it duplicates the original wiring error, even if a heavy gauge secondary wire was used, the frame and return (red) positive harness wiring are "common" therefore if the heavy gauge engine to battery wire connection fails, there is still the potential for the starter current to travel across the head steady wire and burn out the harness unless the head steady wire was attached to the frame and also made of heavy gauge wire.
Having a secondary wire attached to the frame and no head steady wire would still be slightly unsound in my opinion, even with the Isolastics there's no guarantee that the starter current wouldn't find an alternative route to the frame somewhere.

But why would anyone really want a secondary return? If there is an "electrically sound" connection made between the harness return wiring and engine (head steady wire) and another sound connection between the engine and battery positive (heavy gauge positive wire) then that's all the electrical system needs to function, and if you look at any electric start bike or car's battery connections you will normally see only one heavy gauge wire attached to the earth/ground side.

If an owner is intent on fitting a secondary return (harness wire) to the battery then one reasonably safe way to do it (in my opinion) would be to fit the main fuse (or an additional fuse) on the positive side of the battery (positive earth/ground).
 
hobot said:
The engine needs an earth path back to battery just for the spark plug gap current to flow for lots of instants in a row, so does not take much copper or other paths to conduct that brief high voltage but certainly could suck down the spark intensity w/o a nice wire way.
Click to expand...


Fine if you have a pre-MkIII model but that information is basically irrelevant for 850 MkIII with an operational starter motor.

The 850 MkIII wiring has to be approached in a different way because (under certain conditions) there is a potential for the high starter motor current to cross-over to the light gauge harness earth/ground (return) wiring if there is a secondary connection to the battery.
 
Ok more reason for me to stick to kick start only. I've not examined Norton starter paths but hard to read there's a potential for starter current going through isolastic isolated engine mounts and factory didn't provide robust way around. I do have to admit that thumb comensors gives errie sense to get a Cdo going. I tease others brands that theirs lowers their IQ's but that's just not so for Commando's owners.
 
L.A.B. said:
hobot said:
The engine needs an earth path back to battery just for the spark plug gap current to flow for lots of instants in a row, so does not take much copper or other paths to conduct that brief high voltage but certainly could suck down the spark intensity w/o a nice wire way.
Click to expand...


Fine if you have a pre-MkIII model but that information is basically irrelevant for 850 MkIII with an operational starter motor.

The 850 MkIII wiring has to be approached in a different way because (under certain conditions) there is a potential for the high starter motor current to cross-over to the light gauge harness earth/ground (return) wiring if there is a secondary connection to the battery.
Click to expand...

Ya, hobot. Who doesn't know that?
 
Oh, well. This horse has been beaten to death.
I have a T60 with "electric start". It may start if I kick a couple of times to charge the cylinders, then it will start with the electric motor. Or, I can charge the cylinders with the electric motor and it will kick start. I call it "electric assisted start". I do have one push button bike, but I let the battery go dead, so no go nowhere. (Am I starting to write like Hobot?) Then with the crazy left shift one down four up, I was bewildered for a minute or two before I got reoriented to the "modernity" of right brake.
Anywhoo, Norton started first kick again this morning, loaded it into my pick-em up truck, off to Wyoming today after being up late last night changing oils, packing, doing honey-does.
 
christulin said:
I have a T60 with "electric start". It may start if I kick a couple of times to charge the cylinders, then it will start with the electric motor. Or, I can charge the cylinders with the electric motor and it will kick start. I call it "electric assisted start".
Click to expand...

Fit a Tri-Spark ignition, AGM battery and a Dave Madigan starter motor conversion and it'll start first time without any "assist". :)
 
L.A.B. said:
crusadersports said:
So if a secondary earth wire from the positive terminal of the battery is a bad idea, primarily because it can't do the work of the heavy red cable, would it be ok to have secondary earth wire if it was also a heavy gauge cable like the main red cable?

Long red= main earth cable from positive battery terminal to crankcase bolt
Short black= solenoid to battery negative terminal
Long black= solenoid to starter motor


When I asked what the fourth (short red) cable was for, I was told it was to go from the positive terminal to the frame to set up an earth return for things like the indicators, etc. Reviewing all that we've said about a secondary earth being a bad idea, I'm wondering if this would be ok as it's the same gauge as the main red earth cable?
Click to expand...



Not a good idea (and still basically unnecessary in my opinion). Personally I think CNW has got it wrong if they supply a secondary light gauge cable as it duplicates the original wiring error, even if a heavy gauge secondary wire was used, the frame and return (red) positive harness wiring are "common" therefore if the heavy gauge engine to battery wire connection fails, there is still the potential for the starter current to travel across the head steady wire and burn out the harness unless the head steady wire was attached to the frame and also made of heavy gauge wire.
Having a secondary wire attached to the frame and no head steady wire would still be slightly unsound in my opinion, even with the Isolastics there's no guarantee that the starter current wouldn't find an alternative route to the frame somewhere.

But why would anyone really want a secondary return? If there is an "electrically sound" connection made between the harness return wiring and engine (head steady wire) and another sound connection between the engine and battery positive (heavy gauge positive wire) then that's all the electrical system needs to function, and if you look at any electric start bike or car's battery connections you will normally see only one heavy gauge wire attached to the earth/ground side.

If an owner is intent on fitting a secondary return (harness wire) to the battery then one reasonably safe way to do it (in my opinion) would be to fit the main fuse (or an additional fuse) on the positive side of the battery (positive earth/ground).
Click to expand...

Thanks for the explanation LAB-in my case more an owner intent on understanding the full implications of what could be a pretty disastrous electrical error and one that could easily be made with a MKIII just by following the o/e wiring diagram. I'm really grateful for your help with this and it'll leave a thread for others to understand it too: Secondary earth wire from the positive battery terminal is a bad idea with electric start.

Not sure what the favoured brew is in Norfolk, LAB, but I'd be very happy to buy you one if I'm in your neck of the woods one day :D
 
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