![]() That's a 59.5:1 ratio and that helps insure that there's enough voltage to get the job done. By the way, in the Magnetron coil, the primary winding has 74 turns of wire and the secondary has 4400. It's that spike that builds the voltage required in the secondary winding to jump the sparkplug gap and ignite the mixture. Since current (amperage) and voltage are inversely proportional, suddenly stopping the current flow causes the voltage to "spike" as it compensates. As we discussed last month, the sudden break causes the magnetic field to collapse. the flywheel reaches the trigger coil, a second small current is induced in the trigger coil and that current tells the transistor to "turn off", effectively breaking the circuit of the primary winding to ground (Figure 3). When the trailing edge of the magnets in the spark plug gap. As the flywheel continues to rotate that current builds the magnetic field in the secondary winding. Solid-state switching device called a Darlington Transistor, turning the transistor "on." That "on" mode completes the circuit on the primary winding and a current of about 3 amps flows to ground on the crankcase (Figure 2). In addition to the primary and secondary windings, there is a 3rd winding, called the "trigger" coil." When the leading edge of the magnets in the flywheel approach the coil, the magnetic field surrounding those magnets generates a small voltage (about 1 volt) that powers a Here's how: The magnetron coil actually contains 3 separate coils of windings. Well, not only does it work, but also it works better than the old points ever did. It seemed impossible to believe when Briggs told us we could yank out the points and condenser that had served us to well for years and plug that little box in their place. Now let's look at the venerable Briggs & Stratton and its "Magnetron" ignitions system. The largest share of the 80cc and 125cc engines also use some variant of this CDI ignition. ![]() ![]() We also looked at the magneto ignition systems used in the Yamaha KT l00S engine, and took a rather general look at the Capacitive Discharge Ignition systems used on most of the Reed Valve 2 cycles today. Like a transformer, it boosts up the voltage to where we need it to get the job done. That's where the secondary winding, with a lot more "turns" of wire comes in. We have to "muscle it up" to about 5000 volts or so to be able to consistently ignite the compressed fuel/air mixture in the cylinder. But that "potential" doesn't have enough voltage to jump the gap on the sparkplug. You'll recall that we noted that when the magnets in the rotor or flywheel on the crankshaft rotate past the windings of wire in the coil, they induce a voltage in those windings. Last month we began looking at the basic principles that make the ignition system on your engine work. Basic Kart Ignition Explained Printer-friendly format
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