What's the black box for?

Discussion in 'Motorized Bicycle General Discussion' started by brucemg51, Oct 21, 2008.

  1. brucemg51

    brucemg51 New Member

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    It occurred to me while mowing the lawn that the motorbike has an extra part that my lawnmower doesn't. On the single cylinder Briggs & Stratton mower engine, the spark plug wire goes directly from the magneto to the spark plug. Whenever the mag makes a revolution, it induces a spark to the plug. Why do these MB kits have a CDI ignition unit? Is it really necessary for a single cylinder engine? Is it because the lawnmower engine is four stroke rather than two?
     
  2. Nomad

    Nomad New Member

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    yeah!! I'd like to know that too... maybe the lawnmower has an "internal" CDI..
     
  3. Caus-I-Can

    Caus-I-Can New Member

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    i think this is correct dont quote me but a magnetos spark is regulated by the fly wheel so its only option in incresing spark regulation is by increasing speed of motor by of course adding more fuel - hopefully u understand what i mean -

    where as a cdi regulates voltage/ and speed of spark thus working in conjuction with fuel increase to deliver an all over performance improvement--

    p.s. "WARNING' it is very very late were i am so i could be just raving

    IF I'M WRONG PLEASE SOMEONE CORRECT ME SO I GET IT RITE

    peace!!!
     
  4. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Yes, you are raving....

    The mower does have a cdi or points/condenser set up. It's just not open to the eye like a bike engine.

    The cdi on these bikes doesn't change spark timing, intensity, duration or anything else.
     
  5. Caus-I-Can

    Caus-I-Can New Member

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    So what is the differnece and for what reasons
     
  6. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Points are mechanical, CDI does the same thing electronicly.
     
  7. brucemg51

    brucemg51 New Member

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    Yes, now I think I remember seeing that the spark plug on mower engine is connected to a coil.
     

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