Herko Ignition coil on 85 GL1200I

Tom_Charlton · Mar 28, 2015

For the electrical gurus:

I'm replacing the 30yr old Honda Coil set with a Herko coil pack from 97-03 Chrysler Corp. It's about the same size but doesn't have the external resistor. Do I really need to use the Honda resistor with the new coil pack?

I understand the resistor is needed in cars where the ignition may be left on for extended periods without the engine running, but who leaves their Gold Wing ignition on when the motor is not running? Sounds like a quick trip to a dead battery, considering the small capacity of most cycle batteries.

I am replacing the old coil spark wires with graphite center wires unless advised otherwise by this forum.

Thanks in advance for your thoughts.

slabghost · Mar 28, 2015

On a 78 wing with what ignition? Dyna needs to have it's coils matched to last and perform. Other ignitions like Gerex might be okay with them but I think you'll find that without the resistor stuff will start burning out.

joedrum · Mar 28, 2015

ok i know nothing of these coils ..the resistor is for more than just leaving key on its to match cdi box and not ruin a part not made anymore ..so i wouldnt do it

dan filipi · Mar 28, 2015

Do you have some information on this coil pack you could link to?

Dusterdude · Mar 28, 2015

Are they neon coils?

ekvh · Mar 28, 2015

Writing this like I really know, but looking to understand as much as anything.

Coils have a primary winding and secondary winding. Whenever the field collapses a spark will be sent through each, one towards the plug, one towards the ignition. We don't think much of the one in the primary winding because it's small, but it's there. In the 1200 that primary collapse returns to the igniters, pg, and black box. The pieces on the back side of the coil have to be able to take it. The lower the resistance of the coils, the bigger the pop, good for the spark plug side, but not for the ignition side.

That is why the coils have to match the design of the bike. I would suggest you find the ohm of the Herko coils and make sure it's compatible.

You can probably use them, but will need a ballast resistor to protect from the back feed. The negative to using a ballast is that it just negates what the lower ohm coil could do for you. The early bikes use a bypass of the ballast to start the bike when the start button is pushed, but then when the button is released, send it back though the ballast changing it from 12+ volts down to around seven volts.

One idea floating around in my feeble brain is to use a Neon, or Ford EDIS, or GM lower ohm coil with a big enough resistor to protect the ignition side, but then use an rpm window switch to bypass the ballast at higher rpm, say 3500, allowing higher volts to saturate in the coils. This would give better pop at upper rpm, and keep the lower resistance coils from getting too warm since their saturation time is reduced, but still nothing to protect the back feed. Since the saturation time is reduced, the backfeed is also reduced. I have often wondered if the power loss at upper rpm isn't partially spark related.

My electrical theory is limited. It seems the C5 gets around this by using multiple sparks at lower rpm. The early Edis systems used multiple sparks up to a certain rpm, then went to single sparks. A computer can do the math and ensure the saturation time is right for each cycle. Newer cars have a coil sitting for a little bit with no juice so it can't build up too big.

Love to hear from others more knowing than me on this.