A signal source for use in a breakerless ignition system for an internal combustion engine provided outside a bowl-like flywheel of a flywheel type magneto generator, but cooperating with at least one of a plurality of permanent magnets in said magneto generator. The signal generator comprises timing pole means with one end thereof connected to a pole piece of the permanent magnet and with the other end radially extending through and exposed exterior of the cylindrical wall of the bowl-like flywheel in a spaced relationship from the magnet and signal coil means disposed closely adjacent to and outside of said bowl-like flywheel so that said coil means is interlinked with magnetic flux through said timing pole means.
Four pole pieces embedded in the cylindrical periphery of a non-magnetic rotor disk are connected with each of a number of magnets embedded in the disk in circumferentially distributed positions spaced from the rotor shaft and from the disk periphery. Of these pole pieces, one circumferentially interleaved pair is connected with one pole of the magnet by a magnetically conducting yoke strip embedded in one circular face of the disk and the other pair is similarly connected with the other pole of the magnet. The spacing between the first and second pole piece is equal to the spacing between the third and fourth and less than that between the second and third, the latter spacing being equal to the spacing between groups of pole pieces associated with different magnets, for the case of a uniformly timed firing sequence of a multicylinder engine.
