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MKIII Coils Resolution #279046
10/15/09 1:59 am
10/15/09 1:59 am
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CPeery Offline OP
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New to forum. Great place!
Coil question on 850 mkIII:
I am sure there must be a thread here but ...
What is the procedure for switching to 12 volt coils? Would simply unplugging the ballast resistor be required with standard point ignition?

Last edited by CPeery; 10/15/09 8:01 pm.
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Re: MKIII Resolution [Re: CPeery] #279076
10/15/09 11:04 am
10/15/09 11:04 am
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Hamilton, Mass. USA
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Dave Comeau Offline

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do advanced search
norton forum
coils
newer than 3 years
older than 1 week

Not trying to be a jerk.
My only question is why change?
What is the intellectual basis for changing something you don't even know how to do?

Re: MKIII Resolution [Re: Dave Comeau] #279079
10/15/09 11:34 am
10/15/09 11:34 am
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CPeery Offline OP
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Good question. Don't think I'd ever learn without doing something stupid first. Which I am recently prone to do. I think I will just get the right coils now.

Re: MKIII Resolution [Re: CPeery] #279132
10/15/09 4:01 pm
10/15/09 4:01 pm
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MexicoMike Offline
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"What is the intellectual basis for changing something you don't even know how to do?"

Heck, I can't even figure out any intellectual basis for owning/operating a Norton Commando! smile

Re: MKIII Resolution [Re: MexicoMike] #279139
10/15/09 4:09 pm
10/15/09 4:09 pm
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Dave Comeau Offline

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I certainly would not be foolish enough to try and clainm that the norton heavy twin(1949) or commando is the best bike going, but I find it personally interesting to delve into the engineering and manufacturing techniques of yester year under the hard economic conditions right after WWII. The evolution toward the commando is like watching a fish die on the beach and be helpless to help...

If a buddy said get rid of those 6v coils, that would be justification, though not enough in my estimation. If one died and he has a pair of 12v and doesn't want to spend the money on a new 6v, than that's fine too.
It's his bike so if he wants to cut it up with a sawzall and throw it in the dumpster that's his right....I was just curious to see the motivation for the 12 coil change.


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
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87 Serv-Equip 100HP MC brake dynamometer,
Re: MKIII Resolution [Re: CPeery] #279160
10/15/09 6:05 pm
10/15/09 6:05 pm
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Norfolk, UK
L.A.B. Online content
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Originally Posted By: CPeery
Coil question on 850 mkIII:
What is the procedure for switching to 12 volt coils? Would simply unplugging the ballast resistor be required with standard point ignition?


On the Commando 850 MkIII, the 6V coils and ballast resistor are actually there for a purpose, unlike the '71-'74 models.

If you use the starter motor, then it would be better to keep the 6V coils and ballast resistor.

Re: MKIII Resolution [Re: L.A.B.] #279177
10/15/09 7:27 pm
10/15/09 7:27 pm
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CPeery Offline OP
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Thank you. Dandy answers. I mistakenly purchased 12v coils, thinking they might provide more spark. Then when I got around to mounting them I forgot they were 12v (didn't look). Now realize they are wrong. I have no starting issues with them, even with ballast resistor plugged in. Running her up on the road produces some missfire. In looking at wiring diagram it appears that simply unplugging resistors should provide continuous battery voltage - at least after starter has engaged. Thought I'd check here before road test and possibly damaging something and\or purchase of correct units.

Re: MKIII Resolution [Re: CPeery] #279179
10/15/09 7:40 pm
10/15/09 7:40 pm
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Given that you have already changed the coils and that starting is OK, the ballast resistor should be removed.
It must be replaced with a jumper. Or you can jumper around it without physically removing it as an experiment.
That will cure the "running up the road" problem that you mention.

The net effect is that you will have a slightly hotter spark when running than with the 6 volt combination (doesn't really matter) , but not as hot a spark when starting (may matter, but probably not).

You won't damage anything.

Last edited by SBoyd; 10/15/09 7:48 pm.

Stop the insanity.
Re: MKIII Resolution [Re: CPeery] #279186
10/15/09 8:02 pm
10/15/09 8:02 pm
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When the electric starter is operating, the voltage in the electrical system drops, due to the heavy current taken by the starter, so a ballast resistor bypass wire (White/Purple) is normally connected between the starter solenoid and the 6V coils, which supplies the coils with all available battery voltage during starter operation, this has the effect of boosting the coil voltage during electric starting.
If 12V coils are fitted in place of 6V ones, then the ability to momentarily boost coil voltage during electric starting will be lost.

MkIII owners should however be aware that if an electronic ignition system has been fitted in place of the original points, then the White/Purple wire must be disconnected, preferably at both ends.

Re: MKIII Resolution [Re: L.A.B.] #279217
10/15/09 11:10 pm
10/15/09 11:10 pm
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The resistor is there to lower the voltage and keep the points from burning up. If you remove it your points will arc and pit very quickly, I have seen hotwired cars in the 60's burn up a set of points within a day or so.

Re: MKIII Resolution [Re: Alan Prudhomme] #279303
10/16/09 12:25 pm
10/16/09 12:25 pm
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Alan
If you read the original question and CPeery's three posts, you will see that he has replaced the coils with 12 volt versions.
That makes the resistor dysfunctional and it should be removed or jumpered.
If the coils are changed back to 6 volt, then the resistor will need to be used.

The bike will run the same and points last the same either way.


Stop the insanity.
Re: MKIII Resolution [Re: Alan Prudhomme] #279309
10/16/09 12:43 pm
10/16/09 12:43 pm
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Originally Posted By: Alan Prudhomme
The resistor is there to lower the voltage and keep the points from burning up. If you remove it your points will arc and pit very quickly, I have seen hotwired cars in the 60's burn up a set of points within a day or so.


Although it could be said that running a ballast resisted 6V coil system has an additional benefit of reducing points wear, I do not for one moment believe that is why Commandos had one?


The fact that Norton fitted a ballast resistor and 6V coils from 1971 was, as far as I know, done in readiness for the starter motor that the factory intended to fit to the Commando in the old 'magneto' position, however they were never able to get it to work properly, as it was almost completely unreliable and would destroy its drive mechanism, often damaging the timing side crankcase in the process, the idea of fitting the starter was eventually abandoned until the introduction of the electric start 850 MkIII, (hence the need for the blanking plate to cover the empty starter space at the rear of the timing chest on the '71-'72 crankcases).


However, had there been any sigificant benefit in the use of an additional electrical component that could go wrong, then just about every (British?) motorcycle with a 12V electrical system and points ignition surely would have had 6V coils and a ballast resistor?
But this isn't so, and, in fact the only other motorcycle of the period that I can think of, which actually had a ballast resisted 6V points ignition system as standard was the Triumph Trident T160,-because it had an electric starter.

Last edited by L.A.B.; 10/16/09 1:24 pm.
Re: MKIII Resolution [Re: L.A.B.] #279861
10/20/09 1:43 am
10/20/09 1:43 am
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John Healy Online content
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"Although it could be said that running a ballast resisted 6V coil system has an additional benefit of reducing points wear"

The points would see a lot more than 6 or 12 volts if it wasn't for the condensor!

In fact the primary coil wire, which connects to the condensor and points in these ignitions, will see nearly 400 volts when the coil fires the plug! You will see these kind of voltages whether you run six volt coils with ballast resistor or twelve volts coils. In fact without it you would not have a good hot spark at the plug!


Re: MKIII Resolution [Re: John Healy] #279918
10/20/09 1:21 pm
10/20/09 1:21 pm
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Here is a article you might enjoy.....this explaines it all.
http://www.jetav8r.com/Vision/Ignition/CDI.html
You can remove your balast resistor if you want but I am keeping mine in place.

Re: MKIII Resolution [Re: Alan Prudhomme] #279940
10/20/09 4:47 pm
10/20/09 4:47 pm
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Not to beg the question, but if this site explains it all, where in it does it say that using 6 volt coils reduce points wear?

It does clearly explain the use of the resistor to allow full battery voltage when using an electric starter.


Re: MKIII Resolution [Re: John Healy] #279974
10/20/09 6:24 pm
10/20/09 6:24 pm
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Re: MKIII Resolution [Re: John Healy] #279977
10/20/09 9:01 pm
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It doesnt....A 6 volt battery powering the ignition system never did need a resistor. When the automotive companys switched to 12 volts to power the system (starter and ignition) back about 1955 is when the resistor became necesary. It lowers the voltage to between 6 & 8 volts to help with the arking problem the points have. If you think running 2-6volt coils in series will drop the voltage to the points go for it, some people have to learn the hard way The article does mention fast switching transistors which can handle hundreds of volts with no harm to them. That is why you do not need a resistor for electronic ignition systems.
Most of the celenoids I have seen have a terminal built into them to give the ignition system full 12 volts while voltage is going to the starter. If you don't believe me turn the kill button on while you stsrt your MK3 .... it will run until you let go of the start button and disengage the celenoid.
If NORTON VILLERS built the bike to run with a resistor why do you find it so hard to understand. We are talking about points arent we?

Re: MKIII Resolution [Re: L.A.B.] #280007
10/20/09 11:45 pm
10/20/09 11:45 pm
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Dave Comeau Offline

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Don't believe this guy (I don't mean LAB)...or all you are fed on the internet
In the 1970's I used to teach college level electronics. I still work in electronics on a daily basis, quite sucessfully I will add.

"When the points close, current through the coil primary increases from zero to maximum in an exponential manner, rapidly at first, then slowing as the current reaches it's maximum value."

He is clearly describing a capacitor. High current initially.

An inductor impedes current flow initially. Then it slowly builds toward its maximum.

Last edited by Dave Comeau; 10/20/09 11:56 pm.

dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
Re: MKIII Resolution [Re: Dave Comeau] #280010
10/21/09 12:11 am
10/21/09 12:11 am
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Quote:
"When the points close, current through the coil primary increases from zero to maximum in an exponential manner, rapidly at first, then slowing as the current reaches it's maximum value."

He is clearly describing a capacitor. High current initially.

An inductor impedes current flow initially. Then it slowly builds toward its maximum. Dave


Dave
If you re-read the above, you will see that he is saying exactly what you are saying.

Impeding current at first (low current initially), then letting it build. The opposite of describing a capacitor.


Stop the insanity.
Re: MKIII Resolution [Re: Alan Prudhomme] #280023
10/21/09 12:53 am
10/21/09 12:53 am
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Stuart Online content
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Hi Alan,

Originally Posted By: Alan Prudhomme
If you think running 2-6volt coils in series

'Fraid you are mistaken and John and Les are correct. Multiple coils switched by multiple sets of points are wired in parallel - i.e. each coil has its own supply and earth/ground, via its corresponding set of points - not in series, where the coils are connected together +ve to -ve in a 'chain' and the 'chain' has a single supply to one free coil +ve or -ve terminal, with the opposite-polarity free terminal at the other end of the 'chain' being the only one connected to earth/ground.

Originally Posted By: Alan Prudhomme
when the resistor became necesary. It lowers the voltage to between 6 & 8 volts to help with the arking problem the points have.

As it clearly says in the article you've linked, "to prevent point-gap spark a condenser is used". If you look at any automotive wiring diagram with (a) points-switched coil(s), you'll see a condensor (aka 'capacitor' in that article's "basic ignition design" diagram and by Lucas). In any event, reducing from 12V to 6V cannot have any effect on arcing at the points - it is incorrect to consider coils by voltage, a '6V' coil has around half the low-tension resistance of a '12V' coil so the current draw is pretty much the same.

Originally Posted By: Alan Prudhomme
The article does mention fast switching transistors which can handle hundreds of volts with no harm to them. That is why you do not need a resistor for electronic ignition systems.

Certainly on the e.i. most readers are familiar with, 'fraid this is irrelevant. These e.i. (e.g. Boyer-Brandsen, Rita, Trispark for twins, Pazon, etc.) have only one output, so multiple coils must be connected in series; apart from the requirements of the electronics, supplying the e.i. with only 6V would mean each coil would receive only a fraction of its rated l.t. voltage, which severely compromises its ability to produce an h.t. spark.

Originally Posted By: Alan Prudhomme
Most of the celenoids I have seen have a terminal built into them to give the ignition system full 12 volts while voltage is going to the starter. If you don't believe me turn the kill button on while you stsrt your MK3 .... it will run until you let go of the start button and disengage the celenoid.

And your point is? Fwiw, the Lucas M3 starter used on the T160 and T140 doesn't have that terminal on the solenoid, the ballast resistor bypass being supplied from the starter relay instead.

Hth.

Regards,

Re: MKIII Resolution [Re: Alan Prudhomme] #280038
10/21/09 1:53 am
10/21/09 1:53 am
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There seems to be some confusion with D.C.fundamentals in some of the above replies.
To run the same wattage (power) component on 6V,you need twice as much amperage as you would with 12V.
That's twice as many amps (THROUGH THE POINTS) to run a 6V coil compared to a 12V coil.
The voltage drop across the resistor consumes (WASTES) as much energy as the 6V coil consumes. 12v is appled to the series cicuit,but it must still draw the high amperage required to operate the 6V coil.

LOWER-VOLTAGE COIL,+ RESISTOR,+ STARTING BY-PASS is the best thing since sliced bread, for points ignition and a starter motor.(At least for starting anyway;whether you have a 12V system or 6V system).
After startup you are just wasting a lot of your precious charging (very precious on a Brit-bike) to heat up a couple of resistors.
If you have no starter motor,you would just be running double current through the points for nothing.

Re: MKIII Resolution [Re: Pete R - R.I.P.] #280043
10/21/09 3:11 am
10/21/09 3:11 am
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Remember ELI the ICE man?

Re: MKIII Resolution [Re: Stuart] #280098
10/21/09 2:54 pm
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http://wiki.answers.com/Q/What_does_the_Ignition_Coil_Resistor_do
Using the primary windings of the coils as a resistor is not something I would do on my bike....now you are free to do what ever you like to yours. The points are simply a on off switch, the more voltage that passes through them the faster they burn out. There is nothing misterious or high tech here why try to make it so????

Last edited by Alan Prudhomme; 10/21/09 2:54 pm.
Re: MKIII Resolution [Re: Stuart] #280146
10/21/09 6:18 pm
10/21/09 6:18 pm
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Originally Posted By: Stuart
Originally Posted By: Alan Prudhomme
Most of the celenoids I have seen have a terminal built into them to give the ignition system full 12 volts while voltage is going to the starter. If you don't believe me turn the kill button on while you stsrt your MK3 .... it will run until you let go of the start button and disengage the celenoid.

And your point is? Fwiw, the Lucas M3 starter used on the T160 and T140 doesn't have that terminal on the solenoid, the ballast resistor bypass being supplied from the starter relay instead.


I expect Alan meant the Commando 850 Mk3 type 'solenoid' that incorporates a ballast bypass terminal similar to the T160 relay rather than the pre-engaged Lucas M3 starter type of solenoid?

Re: MKIII Resolution [Re: L.A.B.] #280160
10/21/09 7:42 pm
10/21/09 7:42 pm
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Thank you L.A.B.
The point was to show the designers set up a circuit in the celenoid to give full voltage for a much hotter spark DURING CRANKING ONLY as the full voltage (up to 14V) will destroy the contacts of the points in very short order. I have seen coils with resisters built in (if I remember right they had a blue dot on them) that was a long time ago maybe 35-40 years?

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