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Contact Breaker Points

Submitted by les_waller on Thu, 07/04/2022
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Commando

Does it matter which wire from the two contact breakers goes to which connection on the harness, (i.e. can they be reversed) I have been  rewiring my bike and I cant remember which way round the two connections were before I changed the harness.

Submitted by john_holmes on Thu, 07/04/2022

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It will affect the order of which side sparks first, same effect as changing the HT leads over or the 2 feed wires to the coils. This is because points is sequential firing not wasted spark as EI is. With 3 ways to change the order if you get it wrong on one just swap one of the others,

Submitted by les_waller on Thu, 07/04/2022

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Is there an easy way of checking which way is correct and which set of points goes to the correct cylinder at tdc on the firing stroke apart from starting the engine which is not possible at the moment

 

Submitted by john_holmes on Thu, 07/04/2022

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Take the rocker boxes off, the side with both valves closed with the pistons at TDC is the firing side. So the coil wire should match the open set of points wire colour eg black white or black yellow for both on the firing side. 

Submitted by alan_osborn on Thu, 07/04/2022

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Commando on points! Do not worry. just wire everything up ready to go, even check for a spark by ignition on and open each set of points with a loose plug lying on the head. Then if every thing appears in order try starting it. If it starts they are the right way round. If it doesn't start swap them over, it will then start.

All else fails buy electronic.

Submitted by les_waller on Fri, 08/04/2022

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Thanks John, just what  I needed to know.

Alan I will be selling the bike ('71 Roadster) once it is back on the road as I am now 78 years old and I don't think i will be able to cope with it any more. So bearing this in mind is it worth spending money on either a Boyer or similar unit? I.E. will I get any return for the extra outlay?

Submitted by john_holmes on Fri, 08/04/2022

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On a twin the main benefit of EI is the sparks are always 360 degrees apart so when you strobe you only need to do it once and then it does not start to wear points unevenly giving you different timing between the cylinders. You lose at bit in acceleration as the advance is not so aggressive.  

 


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