Failing coil

[Ken4004]

Just found this spark plug tester on eBay, not sure if it’s any good but it looks like a fairly basic device so it’s probably OK.

[Bryanj]

That does not test the spark plug it test wether the coil is giving a good spark

[K2-K6]

Put a spare plug in a lead  and start it with that held to earth, will verify you've got coil output.

[Bryanj]

Better if you remove the cap and see how far the spark will jump from ht lead to head, from old memory 3-4mm is a minimum

[Ken4004]

That does not test the spark plug it test wether the coil is giving a good spark

Yes you are correct I meant to say coils , sorry for the confusion

[Athame57]

I've dug up a coil from the depths of my spares pile and fitted that, all is now fine.  While the spanners where out I put a new starter solenoid in too  as issues had started with that as well.

[McCabe-Thiele (Ted)]

I've dug up a coil from the depths of my spares pile and fitted that, all is now fine.

Could you see any visible cause on the coil you changed such as casing cracks or HT leads cracks?

[Athame57]

Could you see any visible cause on the coil you changed such as casing cracks or HT leads cracks?

I binned it without really looking for those things, the pic is of a different coil, but I did notice something else. The two rectangular protrusions ( I don't know their name) on each end I thought were solid things but are actually many leaves pressed together. When unbolted from the frame these leaves splayed and showed rust. Maybe oxidation caused the failure? 

[Ken4004]

It’s a shame you threw the old coil away I would have liked to have tried to repair it just as a matter of interest.
People would say why bother but I like to know how things fail and why .

If anyone has any coils they are going to junk please let me know thanks on advance.

[Mikep328]

"there have been reports of someDyna units failing, and thats the originals not the knock offs"

Original coils failing after only 50 years...You'd think Honda would have used some decent quality parts! 

[Athame57]

"there have been reports of someDyna units failing, and thats the originals not the knock offs"

Original coils failing after only 50 years...You'd think Honda would have used some decent quality parts! 

Interesting, DSS are offering new coils the same as the originals by the original manufacturer. At £74.00 not cheap and without the mounts, but they sound like an investment, I'm tempted.

[McCabe-Thiele (Ted)]

I have Dyna S coils on my 400, benefit is you can easily replace a lead.
I fitted Hedler coils to my 500 as the leads were toast.
My BiL recommended their electronic ignition system.
I've never understood the logic in the leads being part of the coil.
The DS coils do look a good long term buy.

[Athame57]

I've never understood the logic in the leads being part of the coil.

Perhaps a case of built in Functional obsolescence? It shifts units for them!

[Bryanj]

Its cheaper ted, same as phillips(jis) screws, pennies per bike but millions in production