Weak Spark, ’39 Neptune, model 1A39

[nabmd]

I have a weak spark problem with this motor. The original plug wire had broken off the original coil, so I thought I would try replacing it with an OMC universal coil that appeared to be of similar size. I did have to grind down the center pole to 7/16″ from the original 9/16″, which wasn’t too difficult. I was able to sand down the plastic coating on both sides of the center pole so the flywheel magnet would pass, and bend the pin for the plug wire to the side for clearance. The original laminations appear to have been ground down some by the PO at one end; I’m not sure why. When I hold the laminations inside the flywheel, the gap is not uniform at all 3 spots however. If the center pole touches the inside of the flywheel, the ends have about 1/16″/0.03″ gap. There is no adjustment space on the holes in the laminations or mag plate. I replaced the condenser with an axial capacitor, 22uF. I can feel and see spark when I ground the sparkplug to the powerhead, but it won’t jump 1/4″  gap in open air; and it won’t ignite starter fluid when put together. I did swap the flywheel to another similar Neptune, ’41 11A1, that I have and can get a good spark across 1/4″ gap, so I don’t think the magnet is ‘weak’. I cleaned up the points with acetone, but I can’t completely disassemble the points as the one side is riveted onto the support piece. The OMC coil is ‘good’ per a trusted friend. Any suggestions what to do next?

 

[crosbyman]

what resistance (ohms)  and stability do you get on the secondary (HV) to ground ??    did you replace the plug wire with  solid strand copper wire  (7mm) from coil to boot  ??

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• This reply was modified 3 years, 2 months ago by crosbyman.

[Tubs]

I don’t know if this will help you out any because
I used an old coil I had laying around, not a green
one but I was able to get the coil farther back by
putting slots in the lamination’s for the wires.
(You Tube slide show below.)
You might want to check the wire insulation to
be sure it isn’t damaged.
While the holes aren’t slotted , if the screws are left
snug, adjustments can be made with a hammer to
get the best clearance before tightening.
I never tried to see if a spark would jump a 1/4 inch gap.
The motor started and ran OK.
Tubs.
https://youtu.be/tVvSB5QxMrw

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[nabmd]

Sorry for the delay in replying, life happens. See the pics of plug wire, capacitor, and secondary testing. The secondary testing flickered between 8.29-8.30, but maintained that variation for over 1 minute. I did have to grind down the laminates for the new coil, but my wires were not impinged by the laminates.

[Tubs]

I used a condenser. Do you get a spark with a
spark plug at a normal gap grounded outside
of the motor? What is this? Is there some
liquid tape being used there?This is where a
ignition tester is really helpful as you can
energize the system exposing a leak.
Tubs.

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[nabmd]

That is a pinch mark on the green wire. I think I did it while tapping the laminates out of the coil as I was making final adjustments to the center pole ‘fit’. There is no liquid tape on it; the dark area is shadow in the pic. I don’t see any wire showing through when I move the wire around. I can certainly put liquid tape over it. I do have spark to a grounded plug with 0.03 gap, but it is not a fat, snappy, blue spark. Should I drill out the rivets holding the contact arm and clean all that up with acetone? I’d have to come up with replacement screws and insulators.

[Tubs]

I’d use your meter to check continuity.
That should determine if its necessary
for you to take the points apart.
Tubs.

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

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nabmd

[crosbyman]

the green is no big issue  just  cover the stratch with   some latex glue or liquid tape

carefull with black goo  of any type as some  products carry lots of carbon (to color it black)          carbon can short  HV voltages to ground

they make special  corona (High voltage)  proof silicones to  prevent arcing  …..like they used  on old flyback transformers in tube TV’s  to keep them  from  arcing and  oscillating with a high pitch tone.

btw I have a nagging doubt about these coils with 8Koms  secondaries …….don’t know why ???

I think OEM stuff  is more in the 4-6 Kohms ….. is itdue to  bigger  wire gauge  or  fewer feet … I do not know

 

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• This reply was modified 3 years, 2 months ago by crosbyman.

[nabmd]

I checked the continuity across both ends of the rivet holding the black wire and had perfect continuity. But when I checked the rivet to the clip at the end of the wire I didn’t! So, I took the old insulation of the black wire, cleaned it off with acetone, sanded the strands slightly with 400 grit sandpaper, put liquid tape on it, and now have a spark that jumps 1/4″ gap! I’ll try to get it together this weekend and see if it will start. Thanks for all the suggestions/info.

[crosbyman]

good news  🙂    hopefully  1/4 inch will be enough

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