BSA WIRING DIAGRAM

[Porky]

I am rebuilding my old A65 BSA shooting star.
The wiring use to be positive to earth, it has been changed to negative to earth. The plus in on the coil and the minus to the points.
Boyer Branston says the bike can be wired positive to earth, but the coil on the scetch says black wire from box to coil is on the minus and the plus is to earth, the white wire from the box is now negative to earth. How can it still be a black to a minus on the coil and plus to earth, that will be a dead short or a step up in power and you will burn the box out? Am I stupid or did Branston make a stupid scetch?

[bikerbob]

I am assuming you have an A65 Star Twin as a Shooting Star was a 500cc twin with magneto ignition. If I were you I would wire the bike up as per the BSA manual with positive earth then wire the Boyer system as per their instructions I do not think Boyer will have made a mistake like what you infer. I have an A65 Star Twin with a Pazon electronic system fitted similar to the Boyer and had no problems with the wiring and it runs perfectly.

[L.A.B.]

"Branston" Sounds like you could be in a right pickle! Hopefully, you mean Boyer Bransden? 

I am assuming you have an A65 Star Twin as a Shooting Star was a 500cc twin with magneto ignition.

A BSA "Shooting Star" could also be a 441cc single.

Boyer Branston says the bike can be wired positive to earth, but the coil on the scetch says black wire from box to coil is on the minus and the plus is to earth,

Coil? There should be two coils? Are you sure they sent you a sketch for an A65 Star and not a 441 Shooting Star if you perhaps asked them for a diagram for a "Shooting Star"?

 
The correct Boyer Bransden negative earth/ground diagram suitable for an A65 Star can be found here:

  http://www.britcycle.com/Manuals/331NegGrdInst.pdf


Boyer Box
White (-) to earth/ground.
Red (+) to ignition switch and coil 1(+).
Black to coil 2(-)
Connect coil 1(-) to coil 2(+)   

[bikerbob]

You are right L.A.B. forgot about the single but assuming he has an A65 why would you change from positive earth to negative earth what would be the benefit if any.

[L.A.B.]

You are right L.A.B. forgot about the single but assuming he has an A65 why would you change from positive earth to negative earth what would be the benefit if any.

Well....a negative earth system is more compatible with modern gizmos such as satnavs, or LED lights etc., however I think the main reason is that as negative earth is "the norm" nowadays it is preferred by many owners simply because they are more used to dealing with negative earth systems. 

[bikerbob]

Thanks for taking the time to reply but I will leave my A65 as is positive earth.