Grubee 66cc magneto ignition winding output voltage?

Discussion in '2 Stroke Bicycle Engines & Kits' started by JohnnyCrash, Aug 20, 2012.

  1. JohnnyCrash

    JohnnyCrash New Member

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    Howzitgoin' eh!

    I'm just getting my 66cc China Girl together, and have a used CDI unit I want to use.

    I have tested the magneto with an ohmmeter and it appears good (330 ohms). Rotor magnet is strong too. I'm using a variable autotransformer (variable voltage AC supply) to test the CDI module.

    Now, the CDI unit appears to work well, delivering nice fat sparks with a 'pop' at the 60 Hz line frequency. Thing is, I have to apply about 50 to 60 volts AC to the black and blue wires to fire the spark plug. Plug gap is 0.024" (0.6mm).

    Does this sound right? When I try to start the engine, if there's any problems, I want to know if my CDI module is marginal and needs to be replaced before I start mucking with the rest of the engine, which I have carefully assembled (compression is great, carb cleaned out, no intake or crankcase leaks etc.)

    The Grubee "magneto mystery" page says that the 6 volt lighting coil has ~400 turns of wire, and the ignition winding has ~4000 turns, so since there's 10 times as many turns, the ignition side should be able to produce roughly 60 volts to fire the CDI unit. So, I'm in the ballpark.

    Sound good? I need to know what to expect here and any input from knowledgeable people is much appreciated!

    I bought 2 of these engines for a hundred bucks and pulled both all apart, picking out the best bits for a rebuild, meticulously cleaned, inspected and reassembled a complete engine with considerable care. I'm looking forward to seeing it go. I know I could have saved a lot of time by buying a new kit, but at least I know what I have now, and as far as China Girls go, it seems like one of the higher-class whores :)

    Any ideas about the condition of the CDI unit? Sounds OK to everyone?

    Peace

    Ian
     
  2. 2door

    2door Moderator
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    In my tests I've seen 60 to 90 volts AC from the magneto (blue wire) depending on engine RPM. It sounds like your CDI is in the ball park as far as what it takes to fire it properly.

    By comparison, the white wire will give you something betwen 6 to 9 Volt, AC depending on engine RPM.

    Tom
     
  3. JohnnyCrash

    JohnnyCrash New Member

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    2door,

    Thanks, it's nice to know there's a chance it'll work. 50 volts AC from the variable supply was just enough to make it start firing the plug.

    I installed the ignition system today and the exhaust pipe/muffler, got the rear sprocket and chain on yesterday, I shortened the chain so I didn't have to use the cheesy idler wheel. I used a Grip-Shift handle for the throttle :)

    Because these were used engines (one turned out to be total scrap, good for some spare bits) and I totally dismantled them for overhauling, I've been at this for 5 or 6 weeks.

    Can't wait to see this thing go :)

    Ian
     
  4. JohnnyCrash

    JohnnyCrash New Member

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    Got the engine running today, ignition works just fine! Engine fires well even at very low speed.

    Rock on

    Ian
     
  5. 2door

    2door Moderator
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    Good to hear it, John.
    Have fun and ride safe.

    Tom
     
  6. JohnnyCrash

    JohnnyCrash New Member

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    2door, my name's Ian, actually... JohnnyCrash is my moniker from the Canadian radio control forum, it stems from my R/C flying ability ;)

    As for the bike, it's definitely lots of fun, although I wouldn't quite call these things safe! Hehehe

    Peace

    Ian
     

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