Johnson PO-15 Magneto

[Buccaneer]

I pulled the mag plate off the PO-15 for the first time today.
Glad to see that the coil, points, etc., all looked intact.
There’s one coil with two secondary leads to the spark plugs.
If I remember correctly, to test this type of coil you measure
between the two leads?
That’s what I did, and got a reading of 17.9 ohms across the secondaries,
and .2 on the primary. It has the original style condenser, and it
read at 32 mfd’s.
Q. – Are these readings okay?
Q. – What are you using from a condenser replacement?

Thanks!

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Prepare to be boarded!

[Mumbles]

Your coil should be good but it might be a bit high on the secondary winding. The condenser reading is good to as 0.30 uF was specified for your PO’s condenser. I like the old square caps as they seem to stand up better than modern condensers.

If you ever have to replace it, two of these 0.15 uF Vishay caps from Digikey can be wired up in parallel with good results like I did on this F-70 mag.

http://www.digikey.ca/product-search/en … =bc2608-nd

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[Buccaneer]

Mumbles, thanks for the reply. I was wondering if a person would wire those
caps up in parallel. I have some .20 "orange drop" caps from Digi-Key… wish I would have
ordered a variety pack before!

Prepare to be boarded!

[george-emmanuel]

For some reason I’ve seen PO coils with two different readings on the secondary. Normally you see a reading of around 7-9 but there were some coils with higher readings close to 20. Maybe someone can enlighten me as to why? Anyway, the concern is whether you get a good hot spark.

[Buccaneer]

George, interesting about the coils. I wonder who made these coils?
Hopefully I’ll get the points cleaned tomorrow and see if I got
any spark. I ordered some caps per Mumbles suggestion, but
will try the original square condenser out anyway!
Is the flywheel nut anything special on these PO-15’s?
When I pulled the rope sheave off today I was surprised to see
no flywheel nut!

Prepare to be boarded!

[ftruntz]

The flywheel nut is specific to the PO. (May also be used on other Johnsons of the same era)
FYI. I have used D-90X automotive condensers on my PO with success.

[Buccaneer]

Frank, thanks for the information.
Anyone have a close-up photo of a PO flywheel nut so
I can cobble something together, or look for one?
I’ll research said condenser!
Thanks

UPDATE: Measured for the flywheel nut. Oddball size of course.
9/16" x 18 tpi. Nothing I found in the garage fit.

Prepare to be boarded!

[Buccaneer]

Update, Update: Cleaned up the points, etc., and now have
blue spark. Still have to find a flywheel nut.

The inside of the mag plate was sprayed with something
(as seen in the second photo in this thread) ……
not just the plate….. coils, points…….. everything!
Is this some kind of anti-corrosive that the Military sprayed
on? If so, does that mean my 1950 PO-15 has an earlier
mag from a POLR ?

Thanks.

Prepare to be boarded!

[george-emmanuel]

Send me your mailing address and I’ll send a nut.

George

[Mumbles]

I think it was Garry who once said the green coating was an antibacterial agent? The older mags all seem to have it on them.

Isn’t George a nice guy by offering to help you out with a nut? 😀 It would be a little tricky trying to make one as it has a flange to hold the flywheel down and to also pull on the sheave while removing the flywheel. At least the threads are standard SAE.

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