BSA Owners' Club Workshop Discussions

The BSA Workshop => Twins => Topic started by: chrisx1 on 30 Apr, 2023, 20:30

Title: Boyer Bransden ign.
Post by: chrisx1 on 30 Apr, 2023, 20:30
Is it best to use twin 6 volt coils with the above. What are people's recommendations.
Title: Re: Boyer Bransden ign.
Post by: Gup holland on 30 Apr, 2023, 22:07
I thought it was the recommendation 30 years ago when I installed the Boyer ignition, it never let me down over all these years.
Better spark I believe?

Gr alex
Title: Re: Boyer Bransden ign.
Post by: chrisx1 on 30 Apr, 2023, 23:25
How do you wire the coils?
Title: Re: Boyer Bransden ign.
Post by: Spaceman on 01 May, 2023, 06:30
The B-B Mk IV is designed to work with either a 12 V single or a 12 V twin and therefore requires the same coil resistance for both. This means the single can use a 12 V coil but the twin must use 2 x 6 V coils in series as shown. If you use 2 x 12 V in the latter (as per factory spec), you will end up with at most a weal spark.
Title: Re: Boyer Bransden ign.
Post by: Gup holland on 01 May, 2023, 07:34
This is my mk3 boyer, just for info. Read 4 in general data.

Gr alex
Title: Re: Boyer Bransden ign.
Post by: Spaceman on 01 May, 2023, 07:43
I guess it depends on what is meant by a low compression engine: 6:1 is low compression but is 8:1? As said, with 2 x 12 V coils, the higher series resistance will result in a much weaker spark which might be ok but using 2 x 6 V coils will give more certainty.