12v coils in series or in parallel?

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pierodn

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The two 12 Volt coils must be mounted in series or in parallel? (there is a Boyer Brandsen  E I)
12v + 12v in series = 24 Volt: there is too much voltage to spark plugs?
One of two spark plug destroys the electrode.
What to check? ...
thanks.
Ciao.
Piero
 
For Boyer Bransden ignition, the coils must always be connected in series.

12v + 12v in series = 24 Volt
Click to expand...

No.

Coils in series share voltage.

12V/2 = 6V

So each 12V coil is basically operating at 6V. That is why two 6V coils are recommended.
 
Hi Les,
Thnk you.
After few kilometers one spark plug stops to give current: replaced with a new spark the bike starts fine but after a while it happens again.
What to check?
Ciao.
Piero
 
pierodn said:
After few kilometers one spark plug stops to give current: replaced with a new spark the bike starts fine but after a while it happens again.
Click to expand...

Is the plug that fails always the from same cylinder or connected to the same coil, so is it always the left hand side plug or always the right hand plug that fails, or does the problem affect both cylinders equally?
 
I have the same problem - have change my spark plug already quite a few times... not 100% sure if it's always same side. I believe so
 
L.A.B. said:
pierodn said:
After few kilometers one spark plug stops to give current: replaced with a new spark the bike starts fine but after a while it happens again.
Click to expand...

Is the plug that fails always the from same cylinder or connected to the same coil, so is it always the left hand side plug or always the right hand plug that fails, or does the problem affect both cylinders equally?
Click to expand...

Hi Les,
Both, first one then the other.
Thank you.
Piero
 
pierodn said:
L.A.B. said:
pierodn said:
After few kilometers one spark plug stops to give current: replaced with a new spark the bike starts fine but after a while it happens again.
Click to expand...

Is the plug that fails always the from same cylinder or connected to the same coil, so is it always the left hand side plug or always the right hand plug that fails, or does the problem affect both cylinders equally?
Click to expand...

Hi Les,
Both, first one then the other.
Thank you.
Piero
Click to expand...

I know you'll instantly say "No" but...

Are you sure you're not just using poor quality plugs?

And / or been unlucky to have had a 'bad batch'?

I don't know what spec your motor is, but as an example of my point, I learnt a long time ago that in high CR Teiumph engines, standard time Champions or 'normal' NGKs would break down very quickly. To make matters worse, they wouldn't just fail, but they'd cause intermittent misfires, gradually more difficult starting, power loss etc. I wasted much time investigating carbs and ignition and charging systems due to duff plugs!
Now, I only use the iridium electrode NGK plugs.
 
I use iridium, and have changed a few. and for a change i've tried champion too. same issue.
 
pierodn said:
Both, first one then the other.
Click to expand...


Do you have two 6V coils you could try? The problem could be that the two 12V coils are not producing enough voltage at the plugs.
 
L.A.B. said:
pierodn said:
Both, first one then the other.
Click to expand...


Do you have two 6V coils you could try? The problem could be that the two 12V coils are not producing enough voltage at the plugs.
Click to expand...
Hi Les,
Alberto, a friend of mine, has this problem, he doesnt have two 6 v coils.
But Enrico (Orsonoce) has the same problem with two 6 v coils.
I thought the bike has a not very good ground, may be the coils ground on the frame and dont join a red wire from battery.
I dont know.
Ciao
Piero
 
pierodn said:
Alberto, a friend of mine, has this problem, he doesnt have two 6 v coils.
But Enrico (Orsonoce) has the same problem with two 6 v coils.
I thought the bike has a not very good ground, may be the coils ground on the frame and dont join a red wire from battery.
Click to expand...

Maybe a poor ground connection? See if a temporary ground wire connected between the coils/Boyer and ground (Red, +ve ground) cures the problem?

It is possible for the internal coil windings to short to the casing especially if the casing has been crushed or dented, so check by isolating them from ground.
 
One thing i learned years ago was that the factory always speced plugs that would not melt cylinders when the owners screwwed their bikes. For more genteel riding, use hotter plugs thet specified. Cold plugs foul up when driven quietly.
 
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