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battery polarity M50

Submitted by lloyd_turner on Fri, 11/06/2021
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I'm in the process of sorting out a 1957 M50.  As I received the bike it was hooked up as a Negative earth.  The wiring diagram for this year shows it as a Positive earth.  The wiring is not original and I do not know the history of who's had their fingers in it.  My thoughts are to wire it back to the way the Norton print shows it.  Bike also had a very badly frozen piston.  I have managed to get things apart with out trashing the piston.  The rings are toast though.  Piston is a .040 over.  I would prefer a new piston and ring set but if all I can get are .040 rings I'll go that route and use the piston I have.  Any help will be greatly appreciated.  Thanks Lloyd.

Submitted by ian_soady on Fri, 11/06/2021

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.. both negative and positive earth in the 1950s - my 1952 ES2 came with negative from the factory. For a bike I'm keeping to ride, I prefer to wire them negative earth anyway as that is consistent with modern machinery and helps to reduce brain-fade induced errors. As you say however yours would be positive earth as standard so you may want to keep it like that.

Submitted by niall_topping on Fri, 11/06/2021

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I believe that positive earth vehicle wiring went out of favour because it promotes galvanic corrosion on the salty wet roads of Northern Europe.

Submitted by nicholas_clark on Sat, 12/06/2021

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Hi Lloyd.

If you can't find specific Norton piston rings you should be able to use Triumph 650 piston rings, the bore is 71mm and are readily available. The Triumph rings are, compression 1/16" thick and the oil rings 1/8" thick. I use them in my model 40 and you get two sets for your money as the Triumph is a twin. They would not suit the modern Italian pistons as I think the oil ring in those pistons are thicker than 1/8".

Regards Nick

Thanks Nick, I have found a set of .040 over rings from Steadfast Cycles out of Washington State.  Great advice on the Triumph rings too.  I hope to have all my parts here soon.  The rest of the bike is sorted and ready to go.  Mag is still very good with a nice fat spark.

I'll keep you posted.

 

 


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