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Old 06-25-2009, 01:34 AM
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Junster Junster is offline
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Join Date: Jun 2009
Location: Washington St.
Posts: 446
Default Re: CDI capacitive discharge ignition! what tha!?!

Exactly what 2door said. The white wire coil when you ground it kills the field in the blue wire coil. It's so you don't need to ground out a high voltage wire for killing the motor. Using the white to kill the motor is the way it was made to work.
Put something FUN between your legs..
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Old 06-26-2009, 08:11 PM
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Norman Norman is offline
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Join Date: Jan 2008
Location: pampa texas
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Default Re: CDI capacitive discharge ignition! what tha!?!

the white wire is 2.5 layers on the core of the coil frame it is attached at the start of the winding to the coils frame after 2.5 layers of winding the white wire comes out and also attached to the white wire is all of the smaller gauge of wire wrapped around and over the heaver gauge white wires winding and it comes out as on most a blue wire. I lost count of all the smaller gauge windings but it is almost 1/2" deep on the smaller gauge. you can ground out either the white or blue wire and stop the current from reaching the cdi.
The voltage is ac and the current depends on rpm as it will get higher the faster you crank the engine. There is no trigger on the mag coil I'm thinking the mag coil puts out a pulse and the cdi picks this up to and stores it then triggers the firing coil through the use of the electronics in the cdi.
On most small engines weather 2 or 4 stroke the spark plug fires on every revolution. One spark on the power stroke and one spark on the exhaust stroke if its a 4 stroke one spark is wasted or called a maverick spark. On the 2 stroke it fires every revolution as every revolution is a power stroke.
On a briggs you can change the timing by removing the flywheel key or using an off set key. I prefer to find tdc with a degree wheel then by knowing tdc I can set up the flywheel advanced to fire the mag where ever I want it to fire. With that type of ignition system it will retard at high rpms to I add a little more advance to the setting. I get away from using the key by lapping the flywheel to the crank and using about 75 ftlbs of torque on the flywheel nut. You can't lap the mag rotor to the crank on the china engine but you can use an off set key if you want to experiment with the timing.

Last edited by Norman; 06-26-2009 at 08:15 PM.
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Old 06-26-2009, 09:29 PM
joewlms3 joewlms3 is offline
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Join Date: May 2009
Location: south carolina
Posts: 77
Default Re: CDI capacitive discharge ignition! what tha!?!


the pulse frequency as a componet of the AC wave triggers the spark!

great note on the timing norman! i hadnt even considered it as of yet i havent actually run my motor yet and it is my first one but i had opened the mag cover and looked and my first thought was
"hmmm no timing advance device"
i may just have to mess with that at a later date

im enjoying the forum greatly btw most of the time when i get to discuss engine stuff with someone all the other party ever says is can you fix this for me
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