Its not possible (me as a ateacher at least) to explain a mags operation that can takes books to explain and a lot of basic electrical theory in a paragraph here but hey I will give it a shot.
When a magnet (spinning rotor) passes a coil of wire (mags coil) a voltage is induced across the coils windings and current will flow if a circuit is present via the closed points. If that current flow is interrupted (points suddenly open) the coils magbetic field collapses and induces a higher voltage over in the coils HV secondary since it has many more windings. That HV wants to cause a current flow if theres a path and the HV rises high enough so that theres an arving current flow across the plugs gap via the plug wires and cap and rotor.........
The most common cause of failure is the points are burned or pitted or not gapped properly so check that first. A condensor can go bad and that will kill the spark. If it shorts out that kills the spark. if the kill circuit on the points has a short to case ground, that kills the spark.
If you put an ohm meter on the R x 1 scale on the points to ground it should read zero ohms if the points are closed and they are good and not burned and carboned and all else is good and wired correct. If you open the points youre reading the coils LV primary resistance which may be very low ohms (guess is 0.5 to under 2 ohms???) but it must be continuous and NOTTTTT an open circuit (infinity ohms) if its open the coils LV winding is bad/open.
The HV is present at the coils HV secondary output and passes via the rotor tip out to the caps HV towers.
CHECK THE POINTS,,,,,,CONDENSOR,,,,,COIL FOR ANY BAD/OPEN WINDING,,,,,,,,CHECK THE COILS LV CONTINUITY AND THE RESISTANCES WHEN OPEN AND CLOSED ON THE POINTS AS DESCRIBED ABOVE
Ths takes books to explain so dont feel bad if you still dont understand it.
John T Too long retired EE and rusty on this stuff but still remember the basics
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