Early Johnson Ignition

[Buccaneer]

I popped the flywheel off a 1940 Johnson HD-15 this morning.
Different ignition system than the HD-25’s, for sure.

I’ve read about these systems, and understand it’s
a "one coil setup for an alternate firing twin, using
a grounding plate in the flywheel to determine
which cylinder fires." That being said, I’ve never
worked on one, so I have a few questions 🙂

Q- What’s that black crap all over everything,
and is it original? If so, that means the
condenser hasn’t been changed in the last
77 years 😮

All the wire joints are soldered, i.e., plug wires,
primary coil wire, condenser, etc.
Q. Any tips or precautions about taking everything
apart so I can test the coils, etc?

Q. Anyone know what the condenser and coil specs
should be on this model?

On the coil shoe laminations you can see a gap
between the laminations, but just on one end,
evidently where the coil attaches.
Q. Is this normal, or has it been apart before?

Thanks!

---

Attachments:

Prepare to be boarded!

[steveh]

Hey Buc,

The black stuff is an insulating tar that prevents the coil from sending sparks to the mag plate. You’ll want to preserve as much of that as you can. It does look to me like perhaps the coil laminates have been removed at some point, but I don’t believe that little gap will hurt anything. I’m sure others will chime in…

[Mumbles]

The gap in the lams is normal and is caused by the coils mounting ears. If you take it apart, record the number of lams above and below the coil ears so it goes back together the same way. The brushes ride in brass tubes which can be cleaned with a barrel brush. I think i spun a .22 or .223 caliber one in a drill to do mine. Check your brush holders to. One of mine was burned thru at the bottom and leaking current to ground thru a mounting screw. Also make sure there is continuity between the little brass grounding plate under the flywheel and the flywheel itself as there is a little tiny spring under the plate which might burn out. The wires on my HS-10 had been soldered onto the points to so I took a brass plate with the screws in it off a spare set of HD-TN points so I wouldn’t have to solder them back on. The original condenser was rated at 0.18 uF so I epoxied two Vishay 0.10 caps into the original can to help make it spark again.

It took me a really long time to get the bugs out of this HS-10 mag so I hope yours is better.

[Buccaneer]

Thanks for the replies and nice photos!
Mumbles, are the carbon brush holders
bakelite? I wonder if your engine had
a slight "miss" as it was arching away,
eating a hole in that tower!
I like your "fix" using the TD points
piece to be able to screw your wires
to the points. Guess Johnson didn’t think
they’d ever need worked on!
Lake across the road is almost ice free today,
time to drag the boat home!

Prepare to be boarded!

[joecb]

Good write- up there Mumbles, thanks… worthy of a tech article for the "Outboarder". Those Vishay caps are the best, I love em’ . Got turned on to them by Jeff R from AZ, he did a lot of research on the technical specs of those capacitors and he says that they are ideal for our motors…. and the small physical size lends well to retrofitting them into the old cans should you want to get real authentic looking under the flywheel.

Joe B

[Mumbles]

The brush holders must be Bakelite or something similar as they are hard and one has a piece broken off it. I didn’t want to be too rough with them as they seem fragile. While picking away at the carbon track I could get a feel for the material.

The guy I bought the motor from didn’t tell me it had no spark on one cylinder. ‘It ran good the last time I used it’ scenario. This is my first motor with this style of magneto so figuring out how it worked took a bit of thinking to. It’s actually quite simple once you understand it. Troubleshooting this mag drove me nuts as everything on the mag plate checked out but I couldn’t see the leak on the brush holder. Clear nail polish seems to have fixed that but then there was the burned out ground spring in the flywheel causing issues to so this mag actually had two major problems. A small spring from a Merc float solved the flywheel ground issue.

[Author]

Posts