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I’m still trying to solve the mystery of why my coil conversion is not working out,
trying to use a B&S coil on the Neptune’s twin, opposed cylinder, Eisemann
laminate, while others have supposedly been successful. One person in the club
did this, but his coil was oriented 90 degrees different than mine.
Some Maytag fellows have done this conversion with success, while
one said he had poor low speed spark.
Photos attached tell some of the story.Did some more research, thinking and testing
on the B&S coil conversion on the twin Neptune.Lots of information on Smokstak with people trying
this conversion on their Maytags using the same
Eismann 72 coils.The secondaries on the old Eismann and evidently
the B&S coil I’m attempting to use, Smokstak is
referring to this type as “Pass thru” secondaries,
that is the secondary is not grounded to anything,
and in firing a twin cylinder engine, the spark
travels through one secondary plug wire, through
the spark plug, through the engine block, through
the other spark plug, and back to the coil.This would explain why I was having trouble testing
the B&S coils on the Stevens tester by grounding
one secondary to the laminate, and the other secondary
plug wire to Stevens test lead. It would take high amps
to fire the coil on the tester, and would start arcing
to ground between the coil and laminate.
Pretty sure I’ve tested Opposed, twin cylinder Johnson
in this manner with no problems. Are those coils
designed differently?I found a testing procedure in the Merctronic manual
(have manual, but no tester) that shows testing such
coils by hooking up one secondary to the test lead,
and the other secondary plug wire to the Test Probe lead.
Tried this procedure on my Stevens, and worked great
on the B&S coil mounted on it’s original laminates,
firing the coil stead at 1.5 amps.
When I un-mounted the coil from it’s laminates, the
coil would not test at all.
When I put the B&S coil on the whittled down Eismann laminate,
it started to fire, but not until very high amps. (around 4 amps)What’s the reason for the coil only firing good on it’s original
laminates, not firing at all with no laminates, and very poor
on the Eisman laminates?
I presumed the Stevens was supplying voltage to the primary
circuit and the laminates would not be needed for testing.I re-read all of Mohats articles on magnetos last night,
but alas, I’m still at a loss on what’s going on!Ideas welcomed, brilliance greatly appreciated, lol.
More on this saga previously posted here……
https://aomci.org/forums/topic/1936-37-neptune-ob64a-6-hp-opposed-twin/Thanks!
Prepare to be boarded!
No Tesla here, that is for sure. I guess I would put the BS coil back on its original lamination and restest….If it performs as it did originally, then something(s) about the laminations are different…
One thing that I am noticing is that the winding is offset by 90 degrees on your weisman lamination….And, the outer laminations are farther away from the winding also….
Fleetwin, thanks for the input. I did put the B&S coil back on it’s original lams and it tested good
on the Stevens, so the problem must have something to do with the Eisemann lamminations.
I can’t see how the coil would care about it’s orientation on the lamination, but indeed,
the Briggs lams are a completely different design, and for some reason, have a different
color coating on each half.Prepare to be boarded!
An observation… the B&S laminations apparently form a magnetic flux loop around the coil. That piece of insulating paper in the lamination gap is “invisable” to the magnetic flux. The Eisermann lams do not form the same loop. Now how or if this difference is what’s causing the problem, I can’t answer. Only an observation.
Joe B
Looking at the photo again… try testing the coil on the Eisermann lams with the assembly laying in the flywheel so that the lams and the flywheel magnet form a loop … imitating the loop on the B&S set -up
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