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 Post subject: Coil resistance
PostPosted: Tue May 02, 2017 3:34 am 
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Joined: Thu May 19, 2016 10:55 am
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Hi guys

Recently acquired a new top coil from dbelectrical on eBay.
http://www.ebay.com/itm/NEW-IGNITION-CO ... N7&vxp=mtr

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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 Post subject: Re: Coil resistance
PostPosted: Tue May 02, 2017 5:41 am 
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Joined: Tue Jul 19, 2011 7:49 pm
Posts: 184
Location: Toulouse France
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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 Post subject: Re: Coil resistance
PostPosted: Tue May 02, 2017 8:14 am 
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Joined: Thu Nov 17, 2005 11:12 am
Posts: 358
Location: Leicester, NC
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-Dyna-Mini-Coil-Set-0-5-Ohms-Dual-Output-Towers-/222427128965?hash=item33c9b0a485:g:VTIAAOSwB-1YuExQ&vxp=mtr

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 Post subject: Re: Coil resistance
PostPosted: Tue May 02, 2017 8:17 am 
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Joined: Wed Jul 24, 2013 11:07 pm
Posts: 283
Location: Houston tx
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-Dyna-Mini-Coil-Set-0-5-Ohms-Dual-Output-Towers-/222427128965?hash=item33c9b0a485:g:VTIAAOSwB-1YuExQ&vxp=mtr


hey Rick,would it work on a 350 as well ?.
thanks mark

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 Post subject: Re: Coil resistance
PostPosted: Wed May 03, 2017 3:24 am 
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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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 Post subject: Re: Coil resistance
PostPosted: Wed May 03, 2017 8:04 am 
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Joined: Thu Nov 17, 2005 11:12 am
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Location: Leicester, NC
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-Dyna-Mini-Coil-Set-0-5-Ohms-Dual-Output-Towers-/222427128965?hash=item33c9b0a485:g:VTIAAOSwB-1YuExQ&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.

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