Hi all, this is my first post and my first Norton. The model is a 1975 mk 3 electric start. As far as I can tell it is 99% original and has 6000 miles on the clock from new which I believe is genuine. It has a few electrical gremlins but the most concerning one is the charging system. The warning light assimilator lamp stays on and there seems to be little charge going to the battery. What sort of dc volts should I see at the battery when running? It is fitted with a motobatt battery. It shows 12.8 volts at the battery with the ignition off. I own and have worked with Japanese bikes for almost 50 years and this is very different. Any help or guidance would be greatly appreciated. I am based in South Norfolk.
12.8 V when switched off is…
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Hi Michael. Ignition on…
Hi Michael. Ignition on drops to 12.3. Running no lights picks up to 13v. Lights on 12.7. So I'm assuming that it is charging albeit not a huge amount?
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The charging voltage....
The charging voltage is approx the same for ALL 12V systems, cars new/old and bikes new old.
If in the case of a magneto engine bike then you will get away with a lower voltage but 14.4V is about right for a coil ignition machine. Above 15 V you are getting into trouble, if you are constantly below 13.8 you won't go very far.
As this is a MKIII ie electric start, then it must be over 14v with engine revved up. You cannot use a cheap digital meter to measure the voltage as that will pick up engine interference and read gobbledy gook.
The MkIII has an odd unique charging circuit which is explained on my web site aoservices.co.uk under Alternators/MKIII charging. This is a starting point-read and if still stuck then get in touch directly.
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Hi Alan, thanks for the info…
Hi Alan, thanks for the info. I will read your feature on the website and go from there.
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12.8 V when switched off is fully charged.
What's the voltage at 3500 rpm, lights on and lights off?