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Thread: CB250/350K & Black Bomber Cb450K0 Ignition Coil Repair

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    CB250/350K & Black Bomber Cb450K0 Ignition Coil Repair

    Further to this write-up about Honda ignition coil fixing on

    I have been going through all of the old coils for my bikes and repairing them.
    One thing I have found is that on the early brown/beigey coloured CB250/350K coils, you can replace the HT cables, without the need to solder anything.

    On these coils you first look to see if there is a wooden dowel fitted(possibly bamboo) See pic below. If this is present, you carefully drill it out with a sharp 3 mm drill bit. You then cut away any sealing epoxy around the HT lead, where it enters the coil body. You can then tug on the old lead and it should pull out completely,revealing a metal sharpened spike at the bottom of the hole. A new 7mm HT lead can then be inserted fully into the hole, so that the the spike enters into the central conductor core wires (takes a firm push). Before inserting the HT lead, you coat the the outside of the cable with high strength epoxy adhesive, making sure that none gets onto the metal spike. You can then hammer a sharpened bit of 3mm dowel into the dowel hole, to anchor the HT cable. Some coils don't have this dowel and just rely on the adhesive to retain the HT lead.

    The photo's show stages of repair of an early CB250/350K coil

    The last photo is a grey CB450K0 Bomber coil. On the CB450K0 bomber coils (grey plastic body) and later CB250/350K4 coils (blue plastic body), the HT lead conductor is soldered to a brass post inside the plastic, so you have to use a similar method , as described for Honda/4 coils. so, sorry no quick fix on these.

    The last picture shows CB450K0 Black bomber coil with brass terminal exposed and a new piece of 7mm HT cable soldered to the post, prior to re-potting with epoxy resin adhesive & putty.

    Dowel.jpg Cb250 coil drilled.jpg Spike.jpg
    CB250 with new HT lead.jpg Cb450K0 coil.jpg
    Last edited by ancientdad; 12.10.21 at 5:12 PM.

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    Benevolent Dictator ancientdad's Avatar
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    Moved to Tips and Tricks section

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    Senior Member ballbearian's Avatar
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    Is there a simple bench test before investing time and money?

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