1956 SQ4 Positive Earth Conversion to Negative Earth

General electrical problems
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andy.cossies
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1956 SQ4 Positive Earth Conversion to Negative Earth

Post by andy.cossies »

Hi all, I ordered and received an electronic ignition (pointless distributor conversion) mod for my SQ4 and found I'd screwed up and ordered a negative earth kit (DOH!). Exchanging it would be simple enough apart from the fact that I'm in Australia and Dragonfly are in the UK so there would be a considerable time lag while the postal services do their thing.

An alternative would be to switch the bike from 12v positive earth to 12v negative earth. My query is... what's involved in doing that conversion? Unless I'm mistaken, the generator won't require any attention other than repolarising it for -ve earth, just will need to swap the electronic regulator for a negative earth version and obviously the battery terminal leads.

Is my generator assumption correct? Or will the generator require further attention? The bike was 12v when I got it so unsure if the generator was upgraded or not; but no matter on that front as its never used after dark.

I look forward to reading your collective advice.

Rgds,
Andy
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Roger Gwynn
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Re: 1956 SQ4 Positive Earth Conversion to Negative Earth

Post by Roger Gwynn »

Yes you can do as you suggest. Pretty certain you can achieve this by swopping the field coil wires around.
It easy fairly easy to convert to 12 volt but the full advantage will not be seen unless the armature and field coils are re-wound using a different number of turns and wire diameter. The people who used to wind dynamos for us said that they worked the differences out by trial and error on the E3 dynamo, which took a long time and it wasn't worth it for the the small market for the C35SD.
Roger Gwynn, Membership Secretary, curator of the Machine Register and the works drawings. Director of Draganfly Motorcycles, Craven Equipment and Supreme Motorcycles mostly retired.
andy.cossies
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Re: 1956 SQ4 Positive Earth Conversion to Negative Earth

Post by andy.cossies »

Hi Roger, thx for your reply. The bike is already 12 volt, I just need to convert it from +ve earth to -ve earth. As far as I can tell it'll involve re-polarising the generator for -ve earth and to swap out the regulator for a negative earth version? Is it that easy or am I overlooking something?
Mick D
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Re: 1956 SQ4 Positive Earth Conversion to Negative Earth

Post by Mick D »

Hi

You may need to change the connections to the ammeter too.

Regards Mick
andy.cossies
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Re: 1956 SQ4 Positive Earth Conversion to Negative Earth

Post by andy.cossies »

Mick, good point. I missed that requirement.

Rgds
Andy
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