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When figuring current consumption one needs to consider the duty cycle, the amount of time the points are open and closed when the engine is running. Less point gap equals more dwell time and more current draw. Too much point gap cuts down dwell and current draw but might leave the coil a little short on voltage during high load/rpm conditions.
 

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66Sprint
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Ok, I'm with you mostly on the analogy, but I think we are looking at 2 different visions.

You seem to be looking at the system as it is moving, i.e. the battery charge is changing, and I am looking at a point in time, i.e. the instant points close and the current begins to flow.The current is either flowing or not....ON (flowing) or OFF (not flowing) are the only two possibilities....You can alter the speed at which it flows, which is what this discussion is about......

Theoretically, as your example, checking voltage between the minus side of the coil and B- should be "0" (assuming there is nothing in between [IF the points are closed, there IS a short to B- already "in between", negating any voltage reading].....
And if you check amperage anywhere in the loop, it will be the same (2.6 amps)... YES, With points closed......Assuming Battery + to resistor to coil to points to battery-, .An inline ammeter (wired in anywhere in series with the other components )would read the total circuit Amperage of 2.61.....
If the points are open, then you would have 12 volts to ground anywhere in the circuit, and no amps anywhere......Right?
Not exactly.....12 Volts yes, but:
Tapped into the wire prior to the resistor and connected to B-
(a "dead short") would read infinite Amps....(to battery's output and wire gauge carry limits)
Tapped in after the resistor and then to B- would read 4.0 Amps.....(48 Watts)....
Tapped in with 1.6 Ohm coil ONLY (no resistor)....7.5 Amps....(90 Watts)....
Tapped in after both is the same as inline/series...2.61 Amps....(31.3 Watts)....
 

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Discussion Starter #23
Not exactly.....12 Volts yes, but:
Tapped into the wire prior to the resistor and connected to B-
(a "dead short") would read infinite Amps....(to battery's output and wire gauge carry limits)
Tapped in after the resistor and then to B- would read 4.0 Amps.....(48 Watts)....
Tapped in with 1.6 Ohm coil ONLY (no resistor)....7.5 Amps....(90 Watts)....
Tapped in after both is the same as inline/series...2.61 Amps....(31.3 Watts)....
OK, I have no interest in starting or winning an argument, so lets move back to the original question, and any real life experience relative to it would be appreciated.

Do you see a problem with using a 1.6 ohm coil with ANY value ballast in a points ignition?

Have you used any lo ohm coil with a points ignition?

At this point I can either box this coil up and send it back, or try to make it work, and I'm inclined to give it a shot in the interest of learning something new.
 

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Discussion Starter #24
When figuring current consumption one needs to consider the duty cycle, the amount of time the points are open and closed when the engine is running. Less point gap equals more dwell time and more current draw. Too much point gap cuts down dwell and current draw but might leave the coil a little short on voltage during high load/rpm conditions.
Yes, I have read that.

Also read that the capacitance of the condenser should match the coil saturation time constant (or something like that!), but I have no idea if that would come into play here!
 

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66Sprint
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OK, I have no interest in starting or winning an argument, so lets move back to the original question, and any real life experience relative to it would be appreciated.

Do you see a problem with using a 1.6 ohm coil with ANY value ballast in a points ignition?

Have you used any lo ohm coil with a points ignition?

At this point I can either box this coil up and send it back, or try to make it work, and I'm inclined to give it a shot in the interest of learning something new.
I believe we are actually agreeing that it would present no problems to run with a resistor to match to original Ohms specs, and we both are simply trying to determine IF the spark output will be sufficient....IF the coil is only getting 4.3 volts, I don't believe it will produce a hot enough spark, if at all....If it does get 12 V, it should work fine.......Experimentally is a good way to get that answer, and we can both learn something.....
 

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Discussion Starter #26
I believe we are actually agreeing that it would present no problems to run with a resistor to match to original Ohms specs, and we both are simply trying to determine IF the spark output will be sufficient....IF the coil is only getting 4.3 volts, I don't believe it will produce a hot enough spark, if at all....If it does get 12 V, it should work fine.......Experimentally is a good way to get that answer, and we can both learn something.....
YUP,
I think that's where I'm headed, ...……….my original coil literally melted, I think due to an obvious loose core ground at the mounting rivets.
I've got another old coil from a dream, but the wires are really crunchy, and that's why I bought the new one.
So time for some experimenting and testing with my HF fluke wannabe!
 

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66Sprint
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YUP,
I think that's where I'm headed, ...……….my original coil literally melted, I think due to an obvious loose core ground at the mounting rivets. Nope...Core does not usually HAVE to be grounded...(although sometimes it is in the case of AC fired coils /magneto type ignitions).....More likely it was left powered for too long....
I've got another old coil from a dream, but the wires are really crunchy, and that's why I bought the new one.
So time for some experimenting and testing with my HF fluke wannabe!
see in blue....
 

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Discussion Starter #28
see in blue....
Possible, but I don't remember it (although that doesn't mean anything either!)

The jagged edges of the carbon colored deposits look suspicious though, and the core was well grounded before the rivets holding it to the bracket vibrated loose.

At any rate, even though it tests good, I'm afraid to use it now.
 

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66Sprint
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Possible, but I don't remember it (although that doesn't mean anything either!)

The jagged edges of the carbon colored deposits look suspicious though, and the core was well grounded before the rivets holding it to the bracket vibrated loose.

At any rate, even though it tests good, I'm afraid to use it now.
NONE of the wires in that coil should show continuity to the core....Test/check that as well......
 

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Discussion Starter #30
Just thinking out loud here....what about the ballast in series with the coil for normal running, and install a jumper from the starter side of the solenoid to the coil side of the ballast?

That should provide as much voltage as available when starter button is pushed, and cut out when released?


 

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That would work too. The only thing with that connection would be the distance (as opposed to the already available wiring and space for a relay right near the coils) and the large ring terminal to a small gauge wire at the solenoid, but it would have the same effectiveness

Edit: no it wouldn't work, as the starter motor would be getting feedback from the coil voltage
 

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When the starter solenoid releases and the bike is running, the ballast voltage would be fed back through the starter cable to the starter motor... low amps and volts, but still constantly feeding the brushes in the starter motor trying to make it turn
 

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Discussion Starter #34 (Edited)
When the starter solenoid releases and the bike is running, the ballast voltage would be fed back through the starter cable to the starter motor... low amps and volts, but still constantly feeding the brushes in the starter motor trying to make it turn
Yep, you are right.....I knew it was too easy all along!

It also would disable the "crank with no ignition" feature of the key switch.

I deleted the diagram to prevent anyone from trying it and saying "they saw it on the internet so it must be right"...…………….
and also to prevent future embarrassment!:rolleyes:
 

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66Sprint
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Wire it so an automotive relay separately closes both the solenoid circuit and the jumper circuit when the start button is pushed.....(start button powers relay)......
Releasing the button opens both circuits, so no back-feed effect occurs....Simple, and inexpensive to do....
 

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I would wire the relay trigger wire(#85) to the starter motor side post of the solenoid, the supply for the relay(#30) to the other post(battery side) of the solenoid. The other trigger lead(#86) can go to any convenient ground connection, and relay output (#87) can go to the coil terminal.
 

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Discussion Starter #37
Thanks for the info guys......I've got a couple different resistors coming and will take some readings before deciding which one to use. I've got 2 different oem coils...one reads 4.5 ohms and the other 3.6 and can't find the design spec listed anywhere.
I did find the design ignition load to be 3.5 amps so maybe work back from there.
 

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Discussion Starter #38 (Edited)
Picked up a 1.4 ohm ceramic ballast RU 4 ($4.99) from the local auto parts place, and a 2 ohm 100W aluminum version (2 for $4.99) online.

Had trouble finding specs for the ceramic versions, as they are listed by auto make instead of resistance value, so I just brought my meter with me.

The only ohm/temp spec I could find online for the ceramics was an RU 11 and it listed the "cold" resistance at 0.5 and the "operating" at 1.75!

So who knows what the "operating resistances" of the ones I have are?

At any rate, the manual says points closed, not running amperage should be 3.5, so that would equate to a coil resistance of between 3.4 and 3.6 ohms depending on the supplied voltage (12-12.7V) (Which happens to be the value of the old OEM one I have which is not melted)

So either one of the resistors I have will put the coil + ballast at at least 3 ohms Plus whatever the "operating resistance increase" happens to be.

So I believe one of these will be suitable amperage wise, still to be determined if there will be enough voltage left to adequately fire the coil.

More when the garage temperature increases! It's 25 now outside and the state just put a bunch of #@&^% salt all over the roads!!
 

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For what it's worth, I have been using a ballast resistor on my CD175 for a few years now with no problems at all.

The 6v coil is 2 ohms and draws 3 amps on 6 volts. When I changed to 12v I kept the old coil and fitted a 2 ohm resistor in series. I fitted a small relay from the junk box with its coil in parallel with the starter relay coil. When energised, contacts close and short out the resistor.

The fact that the coil gets extra current when the starter is running guarantees instant starting so it only gets that boost for a fraction of a second. Also remember when the starter motor is running the battery voltage may well fall to nearer 10v so a bit extra for the coil is a good idea.

relay.jpg
 
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