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rex

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  1. Hello - we design, build and repair motorcycle generators, if you didn't already know this. You have stumbled on a happy accident. A points magneto primary winding is typically 200 turns, the accident is that so is a 6 volt AC lighting coil. It gets a bit techy from here on in. These windings have a magnetic polarity and generators are often arranged so the windings go north-south-north-south in a ring. The lighting coil is often wound opposite to the magneto if they sit opposite each other. Why is this of concern? A negative spark ignites the fuel 10% more easily than a positive, so magneto windings are wound and timed to the engine to give a negative spark. If the lighting coil wound opposite to the magneto primary coil, it'll be giving a positive spark. In the real world this makes very little difference, but the designer of the generator will have taken this into account. The really important thing to bear in mind that a lighting coil capable of running more than around 30 watts is going to burn the points and condenser to hell as it will produce way too much power! If the iron core in the lighting coil is the same thickness as the points magneto it'll be roughly the same power output. If the lighting coil iron core is thicker, it will make too much power. People think its the copper wire that determine the power out/put. While this has an effect, its the amount of iron core that determines how much power the copper wire will be able to produce. Magnetos need a magneto type HT coil, which is nothing more than a step up transformer. Automotive coils tend to be 12 volts and their primary resistance is too high to give the best spark when used on a magneto ignition.
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