Neptune magneto question(s)

[tibor]

Hello masters of old outboards!

I have a Neptune 15A1 and an AA1A (1945 and 48) that I just recently acquired. I am not getting a spark in either one. I am not experienced with old magnetos at all, so this may be a trivial question….  however I am reasonably experienced in electronic hobby projects so have a bunch of tools to measure things…

I believe both circuits are correct, nothing is accidentally shorted to ground, etc.  Here is what I measure on the coils and condensers:

Coil 15A1 primary: 0.6 Ohm resistance, 0.73 mH inductance,
Coil 15A1 secondary: 4.8 KOhm, 8.2 H inductance,

Coil AA1A primary: 0.9 Ohm, 3.12 mH,
Coil AA1A scondary: 5.0 KOhm, 9 H inductance,

Condenser 15A1:  217 nF, 180 Ohm ESR,
Condenser AA1A:  215 nF, 1.4 Ohm ESR

Do these numbers look reasonable? I think that the coils are probably good, even though 8 Henry is a very large number for me, who is used to small transformers.

Those ESRs are suspect (to me) on both condensers, even though they match nicely to 0.22 uF capacitance. So I guess my question is, what should I replace first? 🙂

Btw, as I am taking these outboards apart, I cannot help but love the simplicity and elegance of their design.

Thanks a lot in advance for your guidance.

[Sam M.]

I have absolutely no clue about what any of those readings should be, but good troubleshooting advice is to check the simplest things first.

Here are some ideas for simple checks before replacing any parts:

• Are the sparkplugs gapped reasonably?
• Do you have a good ground when checking for spark?
• Are the points clean?
• Is the spark plug wire still in good shape? (No internal or external breaks)
• Are you spinning over the motor quite quickly when testing for spark?  There are ignition systems which work fine when the motor is running but won’t spark if the motor is being spun over too slow.

Hope this helps!

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tibor

[tibor]

Sam, thanks for the quick reply.

I tested with an inline spark tester both with the old and a new plug. I did check the gap on the new plug (0.025). I will clean the points more, not sure what I am looking for. So far I did like 4-5 gentle strokes with some fine sandpaper.

The plug wires are not looking too good, one of them has the boot all cracked up. I will try with a new plug wire again.

For the test I cranked the engine with a pull cord.

[tibor]

Update: I have spark on one of them! Went back and actually cleaned the points with 1000 grit and then a bit of paper with alcohol on it.

The inline tester shows a nice spark. The other has a spark plug wire that is basically destroyed, so I will have to make one and test that one too.

Thanks a lot for the help, it was the “Are the points clean?” issue it looks like.

[Sam M.]

Good to hear!

You said you weren’t sure what to look for with points cleaning but I think you aced it.  Real fine grit sandpaper just to carefully polish the surfaces so they stay flat, and then cleaning out the debris is how to do it.  Alternatively, I think for “official manufacturer authorised maintenance procedures” there are small, fine files made specifically for cleaning points, but I have no experience with them.

Good luck with the other one now!

[joecb]

tibor, good job… nothing succeeds like success!  Getting the points really clean and making near zero ohm contact is essential.

Getting back to your original questions… yes those readings are about what one expect from most coils.  As for the condensers, unless you have a way to test them under some voltage stress they might check OK as far as capacitance but still fail in service. Old condensers are always suspect, best to replace, about any .22 +/_ mf cap will do.

Joe B

[tibor]

Joe, thanks a lot for your advice!

I was just wondering about testing a – what I think would be 450-600 V capacitor – with my epic 9V multimeter 🙂

Now that I have something that is working, it is easier to play around, I will replace the capacitor, make a new plug wire (even this one is iffy, never mind the other one) and as long as I still have spark, I am a happy camper.

 

[seakaye12]

The inline “neon” type of spark tester is fine for showing presence of spark….but they really can’t show strength of spark.  For a more meaningful test you could use one of the adjustable gap spark testers….and look for the spark to be able to jump a gap of 1/4″ or more.

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tibor

[crosbyman]

make certain you capacitors  are rated minimum 600 volts  or more

visit the western region aomci site for a series of articles on capacitors by  mr. Mohat    see articles 1-4  & others

Magazine Articles | Western Reserve Chapter

 

Joining AOMCI has priviledges 🙂

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tibor

[tibor]

Now that I have spark, I am onto the carb. The old gaskets are looking reasonable, came off in one piece. I figured that I should preserve their dimensions anyway. So scanned them, traced them. Attaching it here in case someone else needs them.

These are for the Tillotson carb AC-1C.  <=== NO, see bottom of message please.

The png file is at 96 dpi, basically the rectangular gasket should be 3.5 inches wide after printing (cutting). The thickness of  the original gaskets is ~1/32.

It looks like that I cannot attach the svg (vector) file, is there a way to upload it somehow? That is what one would need for a vinyl cutter.

Edit: I keep confusing the two old motors, these gaskets are for “the other one” that has a Tillotson AJ21A carb. Sorry about the confusion. I will make drawings for the AC-1C one as well.

Also, my old vinyl cutter could not cut through the 1/32 material, so I had to finish with a pair of scissors, felt like losing a battle 🙂 The outline does work and now I have new gaskets on the carb side.

 

 

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Sam M.

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