Topic: Re: johnson lt-10 – Antique Outboard Motor Club,Inc

This topic has 15 replies, 4 voices, and was last updated 7 years ago by Mumbles.

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April 14, 2017 at 5:36 pm #6740
lakeofwoods
Participant
As you can see it sparks across the top with the spark tester. It does eventually spark in the window as well though.

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April 14, 2017 at 5:40 pm #56079
lakeofwoods
Participant
The tester

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April 14, 2017 at 7:34 pm #56086
garry-in-michigan
Participant
Lifetime Member
That looks normal to me. It indicates the resistance across the gap in less than the resistance of the tester. The voltage being developed should be enough to fire the plugs. If one plug does not fire, it is a short or open circuit in one of the external high voltage wires or hardware. . . 😉
April 14, 2017 at 9:55 pm #56094
lakeofwoods
Participant
Okay so if I pick up some plug wire and caps it should jump the plug before that gap ?
April 14, 2017 at 9:57 pm #56095
lakeofwoods
Participant
any idea looking at the picture which side fires top plug ? the wires were cut off when I got it .
April 14, 2017 at 11:04 pm #56100
garry-in-michigan
Participant
Lifetime Member
Turn the flywheel so one piston is at top dead center. Measure the resistance of the spark plug wires. The one with the highest resistance is the one that goes to that cylinder. One spark plug wire measures the coil resistance, the other is shorted by the distributer brush and does not. . . 😆
April 15, 2017 at 1:26 am #56107
Buccaneer
Participant
US Member
Good tip Garry. I was just wondering the same thing on the HD-15 Johnson I was
working on today. I eyed up the grounding contact in the flywheel as I put
the flywheel on, with the top cylinder at TDC, then decided which end of the coil
should be "top". Funny, but later on I found my diagram where I noted which
side of the coil was "top" (according to the plug wire band) and it
was opposite of what I guesstimated. I’ll try your Ohm meter method
tomorrow!

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April 15, 2017 at 3:24 am #56112
lakeofwoods
Participant
I will have to put some new plug wires on it with caps and see if it has spark at the plugs . With the spark tester it sparks up at the coil as seen in the picture but with my meter it shows a open on both sides of the coil on the secondary coils.
April 15, 2017 at 7:17 pm #56127
garry-in-michigan
Participant
Lifetime Member
It would show open to ground from either end of the coil unless the other end was grounded. . . 😀
April 15, 2017 at 8:47 pm #56132
Buccaneer
Participant
US Member
Garry, regarding your "tip" below. I tried it this morning,
and it worked like a charm! Thanks.

quote Garry in Tampa:

Turn the flywheel so one piston is at top dead center. Measure the resistance of the spark plug wires. The one with the highest resistance is the one that goes to that cylinder. One spark plug wire measures the coil resistance, the other is shorted by the distributer brush and does not. . . 😆

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