Dual plugging

Discussion in 'Airheads' started by arbalest, Oct 12, 2021.

  1. arbalest

    arbalest Long timer

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    What would be involved in dual plugging an airhead with Boyer Microdigital ignition?
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  2. dave0

    dave0 Been here awhile

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    Two plug holes and a Boyer for dual plugging. More coils.

    Following, as the R60 keeps asking for another set of plugs. Not sure if the Boyer present (KIT00086) works for dual plugging.
    <EDIT: looked at the Boyer site, KIT0104 is for a dual plug setup. There's also a micropower setup (KIT 0304) using their micropower coils.>

    Maybe call Boyer and ask 'em? I'm horribly lazy.
    #2
  3. Plaka

    Plaka Brevis illi vita est

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    Consult Boyer. If you are using the original advance weights any electronic should drive the dual nose coils but always check.. the weights are easy to modify to change the advance curve if desired. heads need drilling for the lower plugs by someone that knows what they are doing. A 12mm lower plug is desirable. The 14 just doesn't leave a lot of meat around the head>valve unless the head is built up with weld beads on the outside. If it is built up then standard reach plugs can also be used, otherwise short reach plugs are needed. new wires for the lower plugs. I make all my own wires so just buy the extra wire and caps, coil ends.

    For a monoshock the chassis needs some mods to fit the dual coils.
    #3
  4. pommie john

    pommie john Long timer

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    I don’t know about the micro digital Boyer, but I run an analogue Boyer. Instead of a single 3 ohm dual output coil, I use two Dyna 1.5 ohm dual output coils in series.
    The Boyer uses electronic advance, the Bob weights are discarded.
    #4
  5. Plaka

    Plaka Brevis illi vita est

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    I one ever ran points they do not get discarded. They go under the seat w/ instructions in a vac sealed bag for when (not if) the Boyer fails.
    #5
  6. pommie john

    pommie john Long timer

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    I have two Boyers on bikes. One I fitted to my Norton in 1984, one on my airhead which I fitted in the early 90s. Both still running. The only problems were corrosion on connectors and on the Norton, the wires on the stator got brittle after about 15 years service.
    They are a reliable bit of kit.
    #6
  7. Plaka

    Plaka Brevis illi vita est

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    I got 6 years each out of 2 boyers on the same bike. For the money I was satisfied. It was a /5 with mechanical advance and the boyer consisted of a pickup and black box, still used the mechanical advance.. maybe they got better over time?

    As a rule I don't trust electronics overmuch. If travelling far I back up every electronic system somehow.
    #7
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  8. arbalest

    arbalest Long timer

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    Every motorcycle I have owned since my British infatuation has had Boyer ignition. I have never had a failure.
    #8
  9. bmwrench

    bmwrench Long timer Supporter

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    I've rejected them right out if the box, for inconsistent advance curves. Every aftermarket ignition I've installed has failed sooner or later. However, I still install them, if the advance works correctly.
    #9
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  10. Plaka

    Plaka Brevis illi vita est

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    So that infatuation began 6 months ago and you have 6-15 miles and less than 6 months on any of them.

    See where I am coming from?
    #10
  11. arbalest

    arbalest Long timer

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    My first bike was a 72 Honda CL 350. My second bike was a 1972 Triumph 500cc Daytona. I had a brief dalliance with a 72 Kawi H2, next came a 74 Triumph Trident, then a 71 BSA A65, then a 74 Triumph Tiger 5 speed (replaced the 5 speed with a four speed). I loved my 86 Honda CBR1000F. Finally, enlightenment came. I bought an 83 Neval (Dnepr) sidecar rig. After three summers of trying to keep the RPOC motor going. I replaced the motor with a BMW R60 motor with R80 cylinders (yes, the spigots were turned down to 97mm) and R75 heads. My next bike was my current bike, a 76 BMW R90/6, which, after three years as a solo bike, I added a sidecar. I have owned that bike for eight years. It may have been a slight exaggeration to say that ALL my bikes had Boyer ignition. The Japanese bikes did not. Everything else had Boyer ignition. I have been riding since 1972, so, no. I do not see where you are coming from.
    #11
  12. pommie john

    pommie john Long timer

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    Getting back to the original question, Boyer's website has a list of installation instructions which are pretty straightforward. The Micro Digital needs 3 ohms of coils so if you're dual plugging, the usual way to go is two Dyna brown coils wired in series.
    This fires all four plugs at once.

    bmwrench's comment about advance curves is interesting. I heard through the grapevine that they had started using looser tolerance components in their electronics in recent years. ( By which I mean using eg 10% tolerance resistors instead of 1% tolerance parts). I don't know if this is true or hearsay but if it's true it could account for variation in advance curves.
    #12