Re: 1940 Johnson HD-15 Magneto testing

[Buccaneer]

Joe wrote –
When the flywheel spins in real time it grounds one side of secondary automatically if brushes and flywheel tab and no cracks in bakelite and its all working.

That is why I was thinking you could put your flywheel in the position on engine and where coil would normally fire that should kill one cylinder fire if brushes and tab are working. Snake a wire and check with stevens meter.

By doing so your checking both plug wires with stevens meter to see if the other side of coil secondary is grounding out as it should with bakelite brass piece in flywheel . The brass tab did show a correct ground when you bench checked flywheel with omc coil and made sure tab was grounded and no cracks in bakelite. You did get spark with the probe when you got near brass tab but no spark checking bakelite thats a good thing. it means Good Ground on tab and good bakelite no cracks?? Hope that makes since.

I think I understand the above, in that I should simulate "real life" operations of the magneto
grounding system with the flywheel on. I believe there’s a hole in mag plate to snake
a wire through, and if the Stevens doesn’t "light up" when it should, then the grounding system
isn’t working correctly.

With the mag plate on the bench, I did test the continuity of the carbon brushes and their springs today, by hooking a
wire with an aligator clip on each end. One end to the brush and the other end grounded to the
mag plate. (instead of grounding one plug wire to the mag plate) I then fired the coil with the Stevens.
I did this with the other carbon brush as well, not finding any problems, such as a poor
soldering job, etc. While testing this way, I rubbed the spark plug wire end (that had it’s
brush grounded) on the mag plate, and got no arcing, which is good!

One more test to possibly try. Use stevens meter to fire your coil and see if both spark plug wires put out spark with flywheel off.
By checking one plug wire for spark then the other with flywheel off. I bet you a bunch of money that they both fire when one is not grounded and that will help explain the need for the brushes and how important they are for correct ignition results. What kills one side in real time is the brushes grounding one side or doesn’t kill the other side then you get double firing which I think you may have.

I do not believe the Stevens unit will fire the coil "unless" one side of the secondary is grounded, but
when the HD-15 is actually running via the flywheel magnets, and spinning many rpms, I’m
guessing there’s more likely to be out of sequence firing of the coil, is something is amiss??

A zephyr has 4 cylinders 2 coils which means 1 coil has to fire 2 plugs/cylinders at same time but one is one piston is in the tdc position and one in the bottom dead center. Since their is 2 coils on a zephyr 4 cylinders more than likely 2 lobes they alternate all that and don’t need the bakelite contraptaction you have in your flywheel.

I’ve wondered about systems that fire the plug, as you say at BDC, and
how they don’t "upset" they system by lighting off residual fumes.
Don’t even four cycle lawn mower engines fire at BDC?

Check your capacitor for leakage also. Try a good tested condenser with good leakage reuslts. The motor does also sound like a capacitor that may be breaking down. With one side of coil grounded everytime it fires I would guess a good condenser/capacitor is even more critical. It really sounds to me like an ignition issue.

Will pull the cap tomorrow and test it for kicks,
and it will (or a new one) have shrink tube on
the leads when installed.

If you [/b]can’t get it worked out we might try one of my home made red atoms in it since you have a type of distributor using the flywheel and brass tab. I have only had success with the omc engines 2 cylinders 1950-1960ish but both magnets are on one-side of flywheel your magnets are on both sides of flywheel but with the flywheel used for distributor who knows might work. I have heard folks have used them in Zephyrs and they also have multiple magnets.

I hope that helps,
Joe[/quote]
Thanks for all the help Joe. Will report back tomorrow some time!
Bucc

Prepare to be boarded!