Author [NL] [FR] [ES] [DE] [SE] [IT] Ignition Coils...  (Read 1023 times)

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  • Online Mambat

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    Ignition Coils...
    on: Aug 02, 2022, 02.06 pm
    Aug 02, 2022, 02.06 pm
    Hi All

    See attached photos of the coils I have removed.
    On advice from Muddysump as to be a possible cause of my hunting issue at around 3500rpm
    I have not tested the coils, I am not sure how to do that (Any advice appreciated!)
    On visual inspection the one coil has visibile corrosion and the sheath has slipped down.
    What do you guys think?






    Cheers

    Mambat

  • Offline awjdthumper   gb

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    Re: Ignition Coils...
    Reply #1 on: Aug 02, 2022, 04.28 pm
    Aug 02, 2022, 04.28 pm
    Check that the primary winding resistance values are very similar and check that the secondary winding resistances are very similar - if a winding is significantly different from the other two then it may be suspect. Check also for any corrosion inside the plug cap - if there is any the coil may be suspect.
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    Re: Ignition Coils...
    Reply #2 on: Aug 02, 2022, 05.27 pm
    Aug 02, 2022, 05.27 pm
    The earlier ignition coils had a primary resistance of 0.8 - 1.2 Ohm which changed to 1.2 - 1.6 Ohms for Gen 2 according to Haynes. The secondary resistance is the order of 11k but, as said, the real test is if the primary values are all similar and the secondary values are all similar. If one coil has a lower secondary resistance, it could mean shorted windings and a lower output HT voltage.
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    Re: Ignition Coils...
    Reply #3 on: Aug 03, 2022, 06.38 pm
    Aug 03, 2022, 06.38 pm

    Hi Awjdthumper

    Thanks for response, much appreciated.

    I tested the coils today

    Primary:
    Coil 1 - 2
    Coil 2 - 2
    Coil 3 - 2

    Secondary:
    Coil 1 - 11.56
    Coil 2 - 11.60
    Coil 3 - 11.64

    So my primary resistance is out of spec?

     :084:

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    Re: Ignition Coils...
    Reply #4 on: Aug 03, 2022, 07.29 pm
    Aug 03, 2022, 07.29 pm
    Secondary readings are very good at about 11.6 k Ohms. I assume all the primary readings are 2.0 Ohms? The fact that they are all the same would seem to imply they are ok and it may simply be that your DVM is not very accurate at these low resistance levels. If there was a problem with the coils, I think it is more likely to be with the secondary windings because the wire used is much finer than the primary windings and consist of many more turns.

    What is the state of the internal sparking plug contacts?
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  • Offline characticus   scotland

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    Re: Ignition Coils...
    Reply #5 on: Aug 03, 2022, 09.33 pm
    Aug 03, 2022, 09.33 pm
    Note that while DC coil resistance checks will sometimes identify a coil has definitely failed, an ok set of resistance readings does not mean the coil is ok - this test does not identify where the HT insulation is breaking down. Insulation breakdown will result in intermittent misfiring as the coil occasionaly arcs internally or to the cylinder head instead of at the spark plug gap. No easy way to test (that I know of) other than by substitution.

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    Re: Ignition Coils...
    Reply #6 on: Aug 04, 2022, 06.50 am
    Aug 04, 2022, 06.50 am
    That's exactly right. If the coils are suspect, the best you can hope for is to see an anomaly in a resistance value which will point you to which coil is defective. In cars, the ECU is usually capable of detecting the slight change in engine rpm due to misfiring and will even tell you which cylinder it is but bike ECUs don't seem to get fitted with this capability.

    In this case, if a defective coil is still suspected then the only options would be either to bite the bullet and replace all 3 coils or to substitute them in turn with a known good one to see if the problem can be eliminated. 
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    Re: Ignition Coils...
    Reply #7 on: Aug 08, 2022, 04.47 pm
    Aug 08, 2022, 04.47 pm

    What is the state of the internal sparking plug contacts?




    The plugs look good to me? They are a little darker on camera than actual.



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    Re: Ignition Coils...
    Reply #8 on: Aug 08, 2022, 04.48 pm
    Aug 08, 2022, 04.48 pm

    Thanks for advice up till now.

    So my best bet is stumping up and replacing all three coils with new as there is not way to with absolute surety
    take them out the equation?

    I will get prices....

     :006:

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    Re: Ignition Coils...
    Reply #9 on: Aug 08, 2022, 05.38 pm
    Aug 08, 2022, 05.38 pm
    I would try the cheaper route first and start with 3 new spark plugs to eliminate any chance it is one of those breaking down and becoming faulty at a certain set of conditions. :027:
    Also owned my 1979 Bonnie T140E from new!
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