Here’s what I did today to look for problems on the HD-15 magneto.
Tested the .2uf cap on the Stevens, and found "zero" issues with it,
but installed a new one with shrink tubing on one lead for good luck.
I would have tried a different capacitance cap, but all I found was
an empty bag of .15 uf caps 🙁
I then tested the coil on the Stevens, with the mag plate and flywheel installed
on the power head. I snaked a wire thru the bottom of the mag
plate and hooked it to the coil primary lead at the points connection.
The points were separated with a piece of paper, and the capacitor
dis-connected. One spark plug lead was hooked to the Stevens,
and the other hooked to a spark plug with it’s base grounded
to the power head.
The "grounding brushes" on the coil secondary towers appeared
to be doing their job, in that when the cylinder being tested
was near TDC, I’d get spark only from that side of the coil,
hence the other side was grounded properly by the carbon brushes.
When neither brush was being grounded by the brass contact
in the flywheel bakelite plate, I’d get fire from both sides of the
secondary, that is the Stevens would like up, and the spark plug
for the other cylinder.
I noticed that the brass grounding contact in the flywheel
bakelite plate is "not" equidistance between the markings for
Top cylinder TDC, and Bottom cylinder TDC, therefore when
running the Stevens and turning the flywheel it would switch
over from firing only one plug wire sooner as it neared the Top cylinder TDC
than when it neared the Bottom cylinder TDC, or vice-versa.
I did remove the bakelite plate, but I’m 99.9% sure it’s correctly
relocated. 😕
I think I’ll put it all back together and see how it runs, (or if)
and if it’s the same irate running Johnson, then I’ll
try and hook up a timing light with it running and see
what that tells me!
Attachments:
Prepare to be boarded!