THEORIES OF OPERATION
A magneto in a sense consists of two simple circuits,
one called a primary circuit and the other the secondary
circuit. Both circuits have windings which surround the
same iron core and the magnets in the flywheel or rotor
act on both circuits. Current can be induced in each by
changing the magnetism in or around the coils of the
The primary circuit has relatively few turns of heavy wire
and the circuit includes a set of breaker points and a
The secondary circuit has a coil with many turns of
lighter wire which are wound around the out-
side of the primary winding, and includes a spark plug.
There are about 60 turns in the secondary to each turn in
A permanent magnet is mounted in the flywheel or rotor.
As the flywheel rotates, the magnet is brought into
proximity with the coil and core.
The Briggs & Stratton new ignition magneto system
differs from ordinary magnetos in that the voltage
produced is tailored to the needs of the engine. See Fig.
26. The magnet used in this new type is a ceramic
which develops a very high magnetic strength in a very
short distance. The length of this magnet is 3/8" as
compared with the Alnico magnet length of 7/8".