Coil resistance

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torp68
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Coil resistance

#1 Post by torp68 » Tue May 02, 2017 3:34 am

Hi guys

Recently acquired a new top coil from dbelectrical on eBay.
http://www.ebay.com/itm/NEW-IGNITION-CO ... N7&vxp=mtr" onclick="window.open(this.href);return false;

The maintenance manual for the RD500 gives the following values for coil resistance:
Primary Coil Resistance: 0.67 Ohm +/- 20% at 20 degr C
Secondary Coil Resistance: 12 kiloohm +/- 20% at 20 degr C

I tested an original one, and found the values were within the limits above.

The aftermarket coil has the following resistance:
Primary Resistance: 3.2 ohm
Secondary Resistance: 15,6 kiloohm

This means both values are outside what the manual calls for. Is this going to affect the ignition and running of the bike? If so; how?
Everything else on the bike is to original spec., std ignition etc.

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phildu31
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Re: Coil resistance

#2 Post by phildu31 » Tue May 02, 2017 5:41 am

Hi.
Resistance is a measure done with direct current.
It is an easy way to get sure that your coil is not cut off.
Normal operation of a coil is with pulses which are a series of alternate currents.
In this case, the equivalent of resistance is impedance which is not easily measurable.

So don't attach too much importance to the resistance if your values are off limits.

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Rick Lance
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Re: Coil resistance

#3 Post by Rick Lance » Tue May 02, 2017 8:14 am

You have purchased a coil designed for an inductive ignition system that expects 3.2 ohms of resistance to work properly. Your RZ has a Capacitive Discharge ignition which runs with very little resistance (0.5 ohm). This is why tachometers from 4stroke bikes will not function with your RZ. The coil is incorrect for your application. It may run anyway but would not be optimum or even a good idea. You may want to give these aftermarket coils a try. I have used them without excellent results.

http://www.ebay.com/itm/V-Twin-32-9342- ... xQ&vxp=mtr
If I disagree with everyone, that doesn't make me right. If I take the side of only one, it doesn't end the fight. If my position's strong enough from exposure to the light, you may see things my way when we share the same highway.

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two-stroke-brit
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Re: Coil resistance

#4 Post by two-stroke-brit » Tue May 02, 2017 8:17 am

Rick Lance wrote:You have purchased a coil designed for an inductive ignition system that expects 3.2 ohms of resistance to work properly. Your RZ has a Capacitive Discharge ignition which runs with very little resistance (0.5 ohm). This is why tachometers from 4stroke bikes will not function with your RZ. The coil is incorrect for your application. It may run anyway but would not be optimum or even a good idea. You may want to give these aftermarket coils a try. I have used them without excellent results.

http://www.ebay.com/itm/V-Twin-32-9342- ... xQ&vxp=mtr
hey Rick,would it work on a 350 as well ?.
thanks mark
She might not be pretty but always a fun ride !!

torp68
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Re: Coil resistance

#5 Post by torp68 » Wed May 03, 2017 3:24 am

Ok, Rick! Thanks for your advice!! Another item for the return bin then...... :mad:
I guess using the Dyna coil requires a new bracket, so I´ll see if I can find a used item till summers past and it´s back in the garage again!
Again, thanks!!

Oyvind

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Rick Lance
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Re: Coil resistance

#6 Post by Rick Lance » Wed May 03, 2017 8:04 am

two-stroke-brit wrote:
Rick Lance wrote:You have purchased a coil designed for an inductive ignition system that expects 3.2 ohms of resistance to work properly. Your RZ has a Capacitive Discharge ignition which runs with very little resistance (0.5 ohm). This is why tachometers from 4stroke bikes will not function with your RZ. The coil is incorrect for your application. It may run anyway but would not be optimum or even a good idea. You may want to give these aftermarket coils a try. I have used them without excellent results.

http://www.ebay.com/itm/V-Twin-32-9342- ... xQ&vxp=mtr
hey Rick,would it work on a 350 as well ?.
thanks mark
Any bike equipped with CDI including your RZ350 would be a good home for this coil. They are sold individually on eBay.
If I disagree with everyone, that doesn't make me right. If I take the side of only one, it doesn't end the fight. If my position's strong enough from exposure to the light, you may see things my way when we share the same highway.

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