Johnson AD-12 mystery

[63lstrition]

Working on a rebuild of a project my girlfriend picked up. Pretty mint ’58 7.5 hp that turned but had no spark. I will spare you the litany of what we did, but new coils, different condensors, different points, give you the picture of what we tried. We ended up getting spark on only one plug no matter what we did. We also ended up with the flywheel hitting the armature by the coil on the side that was not sparking. She may have seated the flywheel with a hammer when I wasn’t watching. 🙁

After pulling out my hair we thought it might be an issue with the flywheel key having moved and the flywheel not seating correctly. We couldn’t pull the old key without wrecking it, so were are in the process of sourcing the parts we need. I am hoping that a new key, another new coil, and new condensors will do the trick. We shall see once they arrive.

Anyone else have this happen to them? I had 2 "new" old-stock coils in the thing and still only had one spark. New wire on the bad one – one spark. Swap coils – one spark. Then we started having the armature impingement so I thought it was flywheel misalignment. Could the flywheel be off enough that it would not generate a spark on a good coil?

Stumped.

[Buccaneer]

When you swapped coils did the "no-spark follow that same "no spark" coil?
If not, I’d suspect the points not clean or grounded out.
Regarding the rubbing of the flywheel and coil shoes, did
you try loosening the coil bolts and see if they’d move "in"
a little to provide clearance. Hopefully the crankshaft isn’t bent.

Prepare to be boarded!

[63lstrition]

The spark did not follow. 🙁 That would have made the issue less maddening.

Swapped points and made sure they were gapped correctly and mated up well. They would spark on one side but not the other. How can I tell if the non-sparking side is grounding or shorting out?

The flywheel is not hitting the coil itself – it is actually hitting the armature plate. I tried moving the coil back and that had no impact. I then was able to see through the point inspection hole that it was hitting a portion of the armature plate itself. That’s when I figured the key may have moved.

Regarding the crank being bent – I don’t think that is it. We did not have an issue initially with the flywheel hitting the armature plate. I don’t think we did anything that could have bent the top of the crank.

[frankr]

So, you are sure the flywheel is hitting the armature plate, and not the coil? Possibilities of that are pretty few, and the key is not one of them.

Are the armature plate mounting rings assembled correctly? The aluminum ring that goes under the brass ring must be installed flat side up, not tapered side up.

Does the armature plate flop around? In other words, is it broken or badly worn at the center?

The flywheel may be bent from somebody removing it with a puller that grabs the outside rim. Not necessarily you but possibly by somebody in the past. If it is, you need a replacement flywheel.

Since you mentioned the key, I am wondering if the keyway in the shaft or flywheel is battered? That happens from failing to install the flywheel correctly, and destroys the parts. Both tapers must be clean and dry and you must use a torque wrench to tighten the nut to 40-45 foot pounds. Battered keyways affect the magnet and points timing relationship. But not just one set.

The #1 cause of no spark is dirty or mis-adjusted points (assuming parts are all good)

[63lstrition]

Definitely not hitting the coil. It hits the plate before it gets to the coil. Its like the flywheel is sitting down about a 1/16-1/8th inch low. I was thinking about filing a taper on the plate, but figured that is addressing the symptom and not the issue. I will take a picture when I have my hands on it again. It might be dragging on one side, but it hits a hard stop when it hits the spot on the plate. Right now the powerhead is off and in a box while we are waiting for parts, and the girlfriend has everything else in pieces cleaning it for reassembly.

Rings under the plate – I will need to look at them. I removed them after the issue started, but everything seemed good. The armature plate fits well – everything is nice and tight. Motor was in really good shape, just no spark.

I will check the flywheel again for how the keyway looks on it. I am thinking it might not be bent as we didn’t have clearance issues initially, but only after "popping the top" a bunch of times in our odyssey to find spark. Before you ask – i did use a puller that had bolts going into the flywheel and not arms on the outside.

Pretty sure we swapped points from the working to the non-working side with no result.

That is why this is such a mystery. Changing things around should have got us spark. Then suddenly having clearance issues really melted my mind.

[frankr]

With what you just said (sitting too low) that could be an expanded flywheel taper from using an impact wrench on the flywheel nut. OR, as I already suggested the mounting ring upside down, allowing the armature plate to wobble upwards and the flywheel to strike it.

[Mumbles]

You say you used different condensers. Why not install brand new ones as they do go bad? P/N 580321.

[63lstrition]

New condensors are on the parts list.

Never used an impact on the flywheel nut.

[david-bartlett]

Is the flywheel hitting the magneto plate or the laminations of the coils?

Are the screws holding the coils snugged up properly?

[frankr]

quote 63LSTriton:

New condensors are on the parts list.

Never used an impact on the flywheel but.

Understand, I was not saying you did it. But how many others have worked on it over the last 60 years?

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