Johnson HD-15 Magneto issues

[Buccaneer]

I’ve had the HD-15 running a few times since I went thru it,
probably 10 minutes the longest run time, but it never
ran good enough to tune in the carb. It was only
running at higher speeds, and acted like an
ignition problem. I don’t think it was dropping
a cylinder, but can’t be sure, but both plugs
seemed equally "hot" to the touch.
The last few times I tried to run it, after playing
with the mag, looking for things wrong, it’s
only gone "down hill", and the spark may not
be as strong.
I checked it out today, and the best "air gap"
spark jump I can get consistently is only 1/8" +
Previously I swapped the new .17 mfd condenser
for an "orange drop" .20 cap just in case I had
a bad condenser, but guess not.
Retested what I could today …….

-Coil Secondary 6.29 K ohms
Primary .8 K
-Kill Post working as designed
-Flywheel magnets – "So-so to Iffy"
-Flywheel brass grounding contact to "ground", "0 to .7" ohms resistance.
-The carbon brushes have good continuity to the coil,
and not grounded out anywhere.
-New plug wires with good readings at terminals.

Mumbles mentioned in a previous thread
viewtopic.php?t=11555
about taking the bakelite plate (with brass contact)
out of the flywheel and replacing the contact
spring inside.
If you’re listening Mumbles, how to you re-attach this
plate to the flywheel after replacing the spring?
It appears to be held on with three rivets, from the
top of the flywheel, but they don’t go thru the
bakelite plate.

Also, regarding the flywheel magnets, did Johnson
ever have an actual test to measure the required pull or
strength of the magnets?

I spent a fair amount of time on the power head,
new rings, tightening up the crankcase clearances, etc.,
so I’d like to see this one be an actual runner!
Thanks!

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Prepare to be boarded!

[Mumbles]

quote Buccaneer:

If you’re listening Mumbles, how to you re-attach this
plate to the flywheel after replacing the spring?
It appears to be held on with three rivets, from the
top of the flywheel, but they don’t go thru the
bakelite plate.

I drilled just enough of the rivet so the plate would come off the flywheel. A few well placed dollops of epoxy were applied to both surfaces before reassembling it with the new spring in place. Getting everything lined up was tricky so I used a thin piece of wire stuck into one of the rivets to help as a guide. When everything was in place and checked out OK with the ohm meter, I stacked some weights on it while the epoxy cured.

The Johnson brothers probably wouldn’t approve of this fix but it seems to be working so far.

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[Buccaneer]

Thanks Mumbles! It looks like a good plan to me!
I re-charged the flywheel magnets last evening.
For the heck of it, I should re-install it, and
see if the spark improves before I tear the
grounding plate apart.

Prepare to be boarded!

[Buccaneer]

I went ahead this morning a removed the bakelite grounding plate from the
inside of the HD-15 flywheel. The spring is much smaller that I thought
it would be. Only 3/32" diameter and 1/4" long.
It’s non ferrous, so not rusty, but has light oxidation or corrosion
on the spring and contact surface on the flywheel.
I have no spring that tiny, nor non ferrous for that matter,
so I may try cleaning the old one up with a brush on a dremmel.

Prepare to be boarded!

[Mumbles]

That spring is smaller than small! The only thing I could find to replace it was one from a Dark Side float and then I had to shorten it. It’s a good thing I had some extra floats as two of the springs got lost in the process.

Isn’t it always the way the smallest part in a motor is also one of the most important?

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[Buccaneer]

I put the flywheel back on the HD-15 (after cleaning up the grounding
plate spring and epoxying the bakelite plate back in).
My "open air gap" spark tester was set about 1/4".
Spark looked pretty good, so I increased the gap some
more, then no spark. Had to go back down to 1/8" ish
before I’d get spark again.
Tried running it in test barrel. Longest run I could get was
about 20 seconds.
Finally pulled it out of the barrel and on the workbench
vise, via a 2×4. It started up and stayed running, but
it sounded like it was missing. Didn’t bother try tuning
out of water, only ran about 30 seconds.
May take the prop off and try in the test barrel tomorrow.
It had 62 and 64 psi before I took it apart. I installed new
rings and tightened up the crankcase. Not sure if the compression
has improved at all with the new rings, but they were much
"stiffer" than the old ones.
Crankcase halves were sealed with sealer as per the manual.
Hopefully I can get it running long enough for you’ll to listen
to it run, as I’m running out of things to try. The coil "ohms out okay",
but I don’t have another coil to try, nor a proper tester to check the old one
for bad windings. This one may sit quietly on the rack,
never to see a lake again! 😮

Prepare to be boarded!

[Mumbles]

The compression won’t come up much until the rings have seated in the cylinders. A Zephyr I have took at least an hour of steady running before I noticed any rise in compression. Breaking in new rings can take a while. In the old days, they spun the motors somehow in the factory to break them in a bit and I’ve tried it using the lathe and spraying the intake occasionally with fogging oil to keep everything inside happy.

If you are getting frustrated, it’s best to put the motor aside for a while and work on something else. When you come back to this motor refreshed, it will be like a new project and you’ll have it figured out in no time. That works for me everytime!

[Buccaneer]

Mumbles, this HD and I have had quite a bit of
"time-out" already, so I guess a little more
wont hurt, lol.

It’s the "miss" that worries me more than
low compression. I had it running in the barrel
previous, perhaps for 5 to 10 minutes, but
it acted like an ignition problem. At one time
it "wound up" like a Johnson should, but it
didn’t last but a few seconds.

I’ve exhausted everything I can check on the mag.
Anyone know what other model Johnson’s
that may share the same coil as this 1940 twin
cylinder Johnson HD-15, with the single coil?
Thanks.

Prepare to be boarded!

[Buccaneer]

HD-15 Johnson final Update ? 😮

Seeing how it stayed running yesterday "out of water",
I took the prop off and threw it in the test tank.
Got it running long enough to take a video.
It sure sounds like it has an ignition problem to me.
Tried grounding out one spark plug at a time.
It’s hard to tell in the video, but it appeared that the
top cylinder is doing the most work. I later confirmed
that by touching the spark plug bases, and the top
plug was quite a bit warmer than the bottom.
I tried another new plug in the bottom cylinder, but
it ran the same….. crappy!
I didn’t see any water droplets on the plug when I
removed it. I tried running it on the top cylinder
with the bottom plug removed, with the idea of
holding up a cardboard to see if any water was blowing
out, but it wouldn’t stay running long enough on one
cylinder.
I seen no tracing of arcing on the mag plate when
I originally worked on it.
Ideas?
https://youtu.be/aPybyPCCht8

For now it’s sitting in the corner in "TIME OUT"!

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