British ignition help

Discussion in 'Motorbike Technical Discussion' started by Dave Haig, Sep 7, 2003.

  1. Dave Haig

    Dave Haig Guest

    Just fitted a Boyer Bransden MK3 to my BS B50 72MX but can't work
    out how to get it to fire without a battery and buying a rectifier ( was
    energy transfer system with half size stator).
    Was I sold the wrong one or is this just the way? Can it be done without a
    battery? Only two wires from stator and never had a rectifier with standard

    Any help much appreciated. I live far away from major city not much to
    resource help here.


    B50 MX
    Trident 900
    Dave Haig, Sep 7, 2003
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  2. Dave Haig

    Les Guest

    Everything I've ever read about Boyer says you'll have to run a battery to
    use it. That's the main reason I won't use Boyer on my bike.

    '70 TR6R "Layla"
    Les, Sep 8, 2003
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  3. Dave Haig

    Dave H. Guest

    You can, however use a large low-ESR capacitor in place of the battery - BSA
    did this on some of the competition bikes in the 70's. An audio-grade 68000
    uF 25 Volt electrolytic should do the job - damn sight lighter than a
    battery, too! You'll *definitely* need a rectifier, as the Boyer needs DC to
    power it, and AC will kill it dead instantly. The capacitor will go
    *BANG!!!!!!!!!!!!!* and shower you with caustic electrolyte if connected to
    AC, too :eek:)
    Dave H.
    (The engineer formerly known as Homeless)
    Dave H., Sep 8, 2003
  4. Dave Haig

    James Clark Guest

    It goes BANG when the wire slips off of the zener.

    With points, you may be able to continue without
    the capacitor by reconnecting the zener.
    It all depends on the points breaking near a
    voltage peak in alternator output.
    James Clark, Sep 8, 2003
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