Excellent mod for old skool coils..

[ogri48]

Done the wired george coil mod on my z thou tonight. It's such a cheap, good but simple mod, has made a helluva difference .. Basically it's this..
I've just changed my coils for high voltage jobbies, but still didn't have that nice, big,  fat blue spark you want at the plug. Apparently, older wiring gets a bit faulty, builds up resistance etc, so your not getting the full 12v to your coils.checked mine and sure enough, 12.7v at the battery, and only 10.8 at the coils.
So all you do is wire in a relay( I did two, one for each side) so that the 12v permanent feed wire to the coil is now the trigger wire to the relay for a switched direct connection to the battery. And that's it..12.7v at the coils now too.
2 volts on the low tension circuit isn't much, but probably gives a few thousand more on the high tension side...it's certainly given me that nice fat spark I wanted :-)

[chaz]

on some old cars they were fitted with 6 volt coils fed through a resistance wire but when starting got the full 12 volts to get a strong spark if the voltage dropped due to high amps taken by starter motor.

[BBROWN1664]

so you now have a relay chattering away at 2500 clicks per second? (at 5000 revs, one spark every two rotations)

Sounds like a failure waiting to happen.

[ogri48]

Err I don't think so, but I could be wrong...I'm a brickie, not a techie..however..
The low voltage live terminal on the coil powered by the relay is permanently on, its the pulse wire on the other side of the coil that breaks the circuit continuously to create the high voltage in the secondary coil windings as I understand it..

[Skippernick]

Sorry, but what is the point? What does it do?

[ogri48]

The answer is in the original post mate...

[chaz]

as far as I understand it the spark is made when the power is turned off, that is, when the points open, this causes the magnetic field to collapse and it induces a high tension voltage in the secondary windings, but I'm only a brickies labourer?

[ogri48]

Lol well between us we can build houses and fix bikes bud....

[schlumpf]

The high side of the coils is attached permanently to 12V. Normally these 12V come out of the loom, but affected by a severe drop due to cable length, fuses and swiches. The relay makes a direct connection to the battery and gives clean 12V.
The low side of the coils is switched by the ECU, causing the spark.
By my estimate and experience the relay gives a gain of about 2V at the coils.

[rustyrider]

But one day it will still fail when the internal resistance in the switch, connectors, cable or wherever it is losing the 2V increases until there isn't enough volts available to pull the relay in.  Going through the wiring and finding out where you are dropping the volts would have had the same affect, a nice big fat blue spark, but you would have found the breakdown waiting for the most inconvenient time to happen.

[ogri48]

I don't think there is a direct problem as such mate, it's just old wiring. Without replacing the entire loom and related switchgear etc it will be what it is. The relay mod just does as schlumpf says, nice clean direct voltage. All I can tell you is it starts and runs better, and plugs aren't fouling anymore. That's gotta be a good thing

[rustyrider]

To lose 2V there has to be a problem somewhere.  If it was losing 0.1 or 0.2V that could be put down to age but not as much as that.  It might be no more than oxidation on the contacts in the plugs in the loom so unplugging them and plugging them back in again could make a difference. 

[ogri48]

Ok, once it gets colder I'll go through the lot and switch cleaner all the connectors etc.

[schlumpf]

I would agree with ogri. You can't get rid of the voltage drop without replacing the wiring. Aging of all components is the main cause. The lines oxiddate even inside their isolation. Besides, Yamaha did a bad job when designing the wiring. The main supply lines go several times all the way from battery to the front and back due to the many switches and fuses. No margin left if aging comes on top.
One remedy would be to give at least the headlights a separate supply directly from the battery. There are some tutorials circulating. That unloads the other lines for the remaining consumers.
Not forgetting the ground line. There is only one single line carrying the complete current back to the battery. That gives extra ~0.6V of drop.
We have to face the fact that we have to live with these handicaps. And try to minimize the consequences by small improvements, like the relay idea. Of course all connectors should be checked and kept in good condition.

[Skippernick]

OK so you get a bigger spark so what, mine hasn't got this and it works fine.
I don't see the point.

[ogri48]

Gawd you people are argumentative...


I'm happy with my bigger spark, your happy with yours, that's all that matters innit?

[rustyrider]

When it comes to sparks, bigger really is better........

[Dead Eye]

Sounds like a good idea to me and if the worst should happen replacing the relay has to be easier than replacing the loom...

As for getting stranded at the side of the road - that can happen at any time on any bike or car for that matter. It's just a chance and can even be down to human error... you know, like forgetting to turn the fuel tap back on...

Besides as Ogri mentioned, this was for his z thou, not the Fazer. I can't see the Fazers needing something like this at their present age

[BBROWN1664]

The reason for the question was that many coils I have seen have one wire connection going in and the HT lead coming out. The one coming in comes from the points (on older bikers) or the CDI on newer ones. if it is this wire that is being used for energising the relay then your relay will be opening and closing at many thousands of times per minute. They are generally not designed for this and will break sooner rather than later. A better nod would be to retrofit electronic ignition to a bike with points. You used to be able to buy kits for this quite cheaply.

[rustyrider]

The coil(s) will always have 2 wires going in and the HT lead coming out.  There will be a permanent 12V on one side of the coil primary and the other side will be pulsed to ground either by points or an ECU of some sort.  The relay goes into the permanent power side of the coil.  The only exception to this was some older Lambrettas and mopeds that used a generator coil to give the power for the ignition and they had a wire from the generator coil to one side of the points (which were insulated from ground), the other side of the points went to the ignition coil primary with the other side of the primary grounded.

[BBROWN1664]

The coil(s) will always have 2 wires going in and the HT lead coming out.

Not always. Many of the ones I have seen have one wire going in and they are earthed through the chassis. I admit some will have two and will be earthed through the points. It is just dependant on the design.

[ogri48]

It's all good then fellers, we just got our wires crossed ( ha..see what I did there?)