Author Topic: coil test question  (Read 3525 times)

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Offline TwoTired

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Re: coil test question
« Reply #25 on: October 19, 2009, 06:19:19 pm »
Let me know when you find one with those measurements, OK?

Best to report what you find to someone who can make an assessment.  Or, take some electrical courses for 4 years so readings make better sense.

Do look out for hatchet marks on the outside of the coils.  That's a bad sign.


Coil construction:
A wire with a thin insulation is wrapped many times around a steel core.  (call it a primary winding)
Then another wire with thin insulation is wrapped many many more times around that first wrap. (call that a secondary).
Then the whole assembly is molded in plastic, after some wires are soldered to each of the internal wraps.

Copper doesn't deteriorate without exposure to acids or other corrosive materials.
 The thin insulation on internal wires is protected by the plastic outer wrap.
If the outer plastic remains intact, the internals are protected.
If you pull out the small wires, you break internal connections. (999999999)
If you pull out the ignition leads, you break the internal connections. (9999999)

If you throw the coils in a fire, you might melt the internal wire insulation and the windings short out due to the copper wraps touching. (Zero, or near Zero)

What bizarre/contrived scenario can you expect the coils to alter their physical properties?  Copper resistance doesn't change with time alone.

Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline andy8190

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Re: coil test question
« Reply #26 on: October 19, 2009, 06:31:49 pm »
that makes sense, i just didnt know the what makes the coils go bad but that explanation makes it more clear

Offline Alan F.

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Re: coil test question
« Reply #27 on: October 20, 2009, 06:52:33 am »
Remove the spark plug caps from the wires.
Use the Ω 20K meter setting.
measure between plug wire end to plug wire end.  Reading S/B about 15K Ω.
This is the secondary reading.

For the primary reading, set the meter to the Ω 200 scale.
Measure from Yellow (or Blue) to the Black/white wires.  Reading S/B about 4.5 to 5 Ω.

All measurements made with the coils completely disconnected from the bike.

ok so the small wires on coil 1 measure 5.5, large wires 15.4
coil 2 small wires 5.6 and large wires 14.98

Sounds like you've got a good set of spare coils there Andy.
-Alan