Pardon my ignorance, but . . .

Why are magnetos so popular with so called 'hot' engines? What are their advantages and disadvantages?

They sure look the business though.

Just read Dave Beckers post in Readers Rides, and it sparked my question.

Basically, a coil ignition needs time to build up electricity for the spark which is done while the points are closed, therefore the faster the engine is revving the less time is available to build up the spark for the next plug in line.
So, some people use twin point distributors (one set of points and one coil) for numbers one and three and the other set for two and four, therefore increasing the dwell angle on each set of points and allowing twice as long for the spark to build up in the coil for each time it fires.
A magneto doesn't require this time to build up the spark; also a magneto at low revs has an impulse arrangment so that when it is spinning slowly it uses the impulse to intensify the spark when the magneto is not spinning fast enough.
So, if you intend to run the motor at high revs and you require a better spark, a magneto will do the job.
Ray

Ray,

Thanks for the concise explaination. The fog is starting to lift....

Thanks again
Rossco