Ignition coil ohms - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 5 (permalink) Old 07-22-2013, 09:46 PM Thread Starter
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Ignition coil ohms

I apologize if this is a repeat, but I looked everywhere and didn't find the answer to my question.
I recently aquired a 93' VN 750. I'm told, when it's been running a while, it doesn't like to start until it cools down. It also backfires when attempting to start it. Many threads point to possible ignition coils going bad. So, I'm testing the primary windings on both ignition coils to find resistance around 3.2 - 4.2. If I'm reading the manual correct, they are supposed to be 1.8 - 2.2 ohms.
Is this a sign of bad coils? If they're both bad, why would the bike be starting when cooled down?
I plan on replacing the plugs and spark plug wires also.
I don't have a good understanding of electrical components so please be patient with me.
Thanks,
TK
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post #2 of 5 (permalink) Old 07-23-2013, 01:45 AM
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I'm assuming that per the manual you tested with the wires disconnected.

Have you tried testing the coils both hot and cold? I'd be curious to see how different the reading are under both conditions.

I'm not sure if the higher resistance would indicate a bad coil or not. I'm sure someone with better knowledge will chime in soon.
Edit: it is possible that as the coil heats up that its shorting to ground causing a problem. Though if that were the case, I would think it would cause problems while it was still running. not just an issue getting it to start back up.

However, the two most common remedies for hot starting issues are a set of iridium spark plugs as well as pickup coil mod (reducing the gap)

also, check the voltage being delivered to the ignition coils, should be 12V. anything less, and you may need to do the mod for them as well to hook then directly to battery power through a relay to switch on with the ignition.

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Last edited by Ndr; 07-23-2013 at 01:53 AM.
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post #3 of 5 (permalink) Old 07-23-2013, 09:16 AM Thread Starter
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I did test them with wires disconnected, and the coil was cold.
I will definately replace plugs. I found some people are just changing out the coils and wires with Accel Super Coil Kit 4 Cylinder (Two-Coil) Inductive Discharge 140403. I'm wondering if that would be worthwhile along with the pick up coil mod.
Still curious to hear what people think about the higher resistance question for the sake of better understanding.
Thanks for your advice.
TK
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post #4 of 5 (permalink) Old 07-23-2013, 09:28 AM
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unless you have a good ohm meter you will not be able to accurately read such low resistance.

Coils that I have seen go bad are either open or they act intermittantly when hot (the insulation on the coils breaks down)

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post #5 of 5 (permalink) Old 07-23-2013, 10:59 AM
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Quote:
Originally Posted by TK73 View Post
I did test them with wires disconnected, and the coil was cold.
I will definately replace plugs. I found some people are just changing out the coils and wires with Accel Super Coil Kit 4 Cylinder (Two-Coil) Inductive Discharge 140403. I'm wondering if that would be worthwhile along with the pick up coil mod.
Still curious to hear what people think about the higher resistance question for the sake of better understanding.
Thanks for your advice.
TK
I am running the Acel super coils. I can't tell you if it was a noticeable upgrade our not because I did the pickup coil mod, earshave and added a ignatech ignition control box all at the same time. I do know my bike runs a lot better with all these mods done.
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