Author Topic: Coil fix CB250/350K and CB450K0  (Read 209 times)

Offline AshimotoK0

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Coil fix CB250/350K and CB450K0
« on: December 10, 2021, 04:44:10 PM »
Further to this write-up about Honda ignition coil fixing:-

https://www.dropbox.com/s/x0a4fcpmrwm3l19/Ignition%20coil%20fix.doc?dl=0

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/beigy coloured CB250/350K coils, you can repllace 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 3mm 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.

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Picture shows Dowel location

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Dowel drilled out and old HT lead removed

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You can just make out the metal spike at the bottom of the hole

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This shows a new HT lead inserted


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.
 
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This is a 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.

« Last Edit: December 10, 2021, 04:46:46 PM by AshimotoK0 »
“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

Offline AshimotoK0

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Re: Coil fix CB250/350K and CB450K0
« Reply #1 on: December 12, 2021, 05:17:16 PM »
Just found that on the 'TEC' CB250K4 type ignition coil the original HT lead was made by Daiichi.

Modern Daiichi electrical parts get a bad press due to Chinese rip-offs but this proves that the companies products were used in Honda OEM electrical parts in the 1970's

“Alright friends, you have seen the heavy groups, now you will see morning maniac music. Believe me, yeah. It’s a new dawn.” Grace Slick, Woodstock '69 .. In the year of the Sandcast.

 

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