SOHC.co.uk Forums > CB350/400
Arcing points
K2-K6:
--- Quote from: Aye Gee 1977 on March 23, 2024, 09:46:53 AM ---Thanks to all. I accept the condenser is the most likely culprit, and I'll check again. It's just that having tried three separate condensers, I was looking for another possibility.
The plug caps could be renewed; at this stage I can't quite see how an issue on the HT side can cause a problem on the LT side - but maybe it can!
--- End quote ---
Emphatically yes, and called back EMF or sometime referred to as "ringing" in which the point when the plug gap is breached by ionisation in crossing the stratified charge in the combustion chamber, the the whole circuit, HT & LT are affected.
This effect is utilised to drive a longer period of spark duration as the entire system ricochet back and forth between the condenser (capacitor) and the plug gap. Defective condenser and it'll jump the points gap, significantly shifted resistance from HT side in variance from specification, can give compromised performance.
https://nationalmaglab.org/magnet-academy/watch-play/interactive-tutorials/ignition-coil/#:~:text=The%20collapsing%20field%20also%20induces,spark%20across%20the%20knife%20switch. Mentioned here.
McCabe-Thiele (Ted):
The back Electro Motive Force (EMF) doing it best to maintain an electrical circuit as it is switched off.
Takes me back to A level Physics.
K2-K6:
The points can register up near 400v too in this event, needs competent condenser to handle that feedback loop.
Mikep328:
FWIW, on my Norton Commando a set of ORGINAL condensers - now fifty, yes FIFTY...yep you read that right, 50 years old(!) produce a tiny spark at the points. I replaced them with new condensers a couple of years ago "just because" and the spark was much bigger. I put the originals back in! Admittedly, this is just one sample which is of no statistical significance but I have to admit it put me in the "They don't make 'em like they used to" camp! :) Same is true of points... :(
McCabe-Thiele (Ted):
I found this interesting - not just bikes that have issues with condenser quality.
https://www.physicsforums.com/threads/death-of-a-condenser-with-autopsy.877969/
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