No matter the scheme, one must to retard timing to start engine

Lawn mower engines, etc, that use an "electronic module" in place of
points and condenser, advance timing auto-magically

These "electronic modules" are cleverly simple, but require a
carefully
designed permanent magnet and magnetic circuit

(rate of rise of generated voltage is quicker at higher RPM's, thus
advancing the timing of spark)

One can eliminate the "electronic module", by making a simple
permanent
magnet high voltage generator, but you will not be able to precisely
time the initial spark

This latter approach is what I've been thinking about for a direct
injection approach(Wherein all one needs is a source of ignition,
that is present at the start of injection)

JCP

Aircraft engines don't retard the timing to start the engine
The prop is a large flywheel

Paul Lamar

Paul:

The mechanical impulse mechanism in one mag does the retard function !
At times you scare me !

JCP

I knew somebody was going to mention the impulse coupling :)
Yes but that is not exactly a retard system It does start at TDC and
it is designed give a strong spark for starting. Not all magnetos
or aircraft engines have impulse couplings. There are several other
methods for doing the same thing that do not retard the aircraft
magneto timing.

On the other hand as I recall the Model T had something like
a manual retard lever so the engine was easier to hand crank

Paul Lamar



The impulse coupling and the retard breaker both force the timing to
at least TDC if not later - eliminating kickback.  The peak pulse
pressure must happen after TDC and at cranking RPM, that means a very
small amount of advance will cause kickback..


Matt-

It is easy to rotate the coils 20 degrees.
Some of these lawn mower systems I am finding seem to be
very similar to this super simple system. Coil and trigger
appear to be combined in one unit.

Paul Lamar