CDI capacitive discharge ignition! what tha!?!

CDI's sometimes use an external electronic trigger, but never off of a points set that I know of.. 2 strokes don't need that kind of timing because they fire every revoloution....

the magneto creates a signal and power that the CDI can use, the CDI uses a capacitor and a resistor to time the energy transfered into the primary windings, then when it fully discharges, it collapses into the secondarys and sparks..

2 strokes don't even need any form of ignition box or timing system.. many chain saws and weed eaters just run off the magneto

has anyone every tried to run engine off of just the magneto on our 2-strokes?

the resistor and capacitor are what times it, as well as the position of the magneto coil to the fly magnet, as it will generate electricity only once per revoloution and at the same degree on the crankshaft rotation

Cabinfever1977 said:

has anyone every tried to run engine off of just the magneto on our 2-strokes?

Click to expand...

I don't think the China 2 strokes setup could fire that way, theoretically it is possible, but I'm pretty sure the magneto coils are wound diffrently that those that fire directly.. it would take a diffrent coil I'm pretty sure, but it ~could~ be done

the third wire is a second ground. designed for a kill switch but it does provide 6v that you can sample from for lighting..

the crankshaft has 1 magnet.. there is 1 set of windings in the coil, it's all in how it's wired

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.

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.
Norman