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Wico OC Mag Question

Peter Holmander

Subscriber
Age
71
Last Subscription Date
12/23/2019
I have a Wico OC that is putting out what I think is a weak spark. The spark looks like a dull yellow. Is that normal, or should it be blue? Anything I can do to improve the spark? There is plenty of info on the net about Wico mags, but not much at all about the OC model. I looked into having it rebuilt, but no luck on that either. I found one place that will do an outright exchange for a rebuilt unit. Hate to spend the money on something I can fix myself with a little help.
 

Kirk Taylor

Registered
Re: Wico OC Mag question

I have a Wico OC that is putting out what I think is a weak spark. The spark looks like a dull yellow. Is that normal, or should it be blue? Anything I can do to improve the spark? There is plenty of info on the net about Wico mags, but not much at all about the OC model. I looked into having it rebuilt, but no luck on that either. I found one place that will do an outright exchange for a rebuilt unit. Hate to spend the money on something I can fix myself with a little help.
The WICO "OC" is little more than an "EK" on steroids. The biggest difference is the drive mechanism. A properly functioning "OC" will easily spark across a ¼" gap and will usually do at least ⅜". I would be reluctant to stretch a spark gap that far merely because of the voltage stress that it puts on the 100-year-old insulation. On a clean spark plug in a darkened room, you should be seeing a nice fat spark; "OC" mags are not wimpy. The "OC" does have a condenser in it. That would be a place to look if you're having trouble. Check the points for oil and corrosion as well as gap setting, and make sure the drive mechanism isn't sluggish. I have a vague recollection of seeing a service manual for the "OC". I'll see if I can locate it.

I found the "OC" manual. Here's a link to it:
https://oldcroak.com/wico-oc-magneto-service-manual/
 
Last edited:

Mitch Malcolm

Sponsor
Age
65
Last Subscription Date
01/14/2020
Re: Wico OC Mag question

Any OC Wico magneto has to be capable of jumping a 1/2" air gap and you should be able to hear the spark jump. That is what is necessary for the big engines they are found on and if its not blue you have a issue with your points or condenser . If you are only getting a weak spark that only jumps 1/4 " you have a coil that is bad. Good luck, Mitch
 

Kirk Taylor

Registered
Re: Wico OC Mag question

Any OC Wico magneto has to be capable of jumping a 1/2" air gap and you should be able to hear the spark jump. That is what is necessary for the big engines they are found on and if its not blue you have a issue with your points or condenser . If you are only getting a weak spark that only jumps 1/4 " you have a coil that is bad. Good luck, Mitch
Thanks, Mitch.
I didn't know that the "OC" mags were required to jump that far and never purposely pushed one to that point. I do know that they are quite snappy when they're working as they should.
Do you know, off-hand, the capacitance of the condenser; I never measured one? Just curious.

Kirk
 

Andrew Mackey

Moderator
Last Subscription Date
05/14/2017
Re: Wico OC Mag question

I would check the points for cleanliness, and also all contacts for crrosion. i would replace the condenser too.
 

Peter Holmander

Subscriber
Age
71
Last Subscription Date
12/23/2019
Thanks for all the great responses !! Does there have to be a spark plug to test the spark strength, of can you just short it to a common ground? I was told it's not good for any magneto to not have a path for the current to flow to when testing it.

---------- Post added at 08:43:55 AM ---------- Previous post was at 08:39:41 AM ----------

Thanks for the link to the OC manual Kirk !! I have one, but the one you posted is better. Much more legible.
 

Kirk Taylor

Registered
Thanks for all the great responses !! Does there have to be a spark plug to test the spark strength, of can you just short it to a common ground? I was told it's not good for any magneto to not have a path for the current to flow to when testing it.

---------- Post added at 08:43:55 AM ---------- Previous post was at 08:39:41 AM ----------

Thanks for the link to the OC manual Kirk !! I have one, but the one you posted is better. Much more legible.
A spark gap is a spacing between the "hot" and the "ground". A spark plug is just a fixed gap. To check the spark length, space the end of the spark plug wire a certain distance from the magneto case and snap the mag. If the mag has to jump a ½" gap, then space the plug wire ½" away from the case. (Yes, electrode shape has some bearing on attainable spark length, but that isn't overly relevant, here.)
You are correct in that a magneto needs a path to ground. You will be providing that path by setting a gap. If you merely let the plug wire hang out in the middle of nowhere, you create a spark gap that is grossly beyond the limits of the magneto. High voltage tends to find the easiest path. If that path is through the insulation, then that's the way it will go. Unfortunately, the insulation in our old mags is not self-healing and is not robust enough to withstand the voltage capability of the mag and is quickly destroyed.
 
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