Paul,  The Briggs and stratton 206 cc  5HP flathead as used on WKA
gokarts
has an aluminum flywheel and operates up to the 13,600 RPM limit of the
construction rule book. The solid state control is built into the
coil.  Put
two coils per flywheel for two plugs and two stacked flywheels for four
plugs. There is weight which can be turned off the  aluminum flywheel as
well as the cooling fan fins. Mount the two flywheels back to back on a
common hub.  For another choice don't forget the Onan used on motor home
generators and riding lawnmowers.which are 180 degree opposed two
cylinder
engines. I have had trouble with the Onan coil wires unscrewing from the
coil post and don't know what RPM it could be safely operated. The
parts are
also larger than the gokart magneto and the onan is not solid state (has
points). The Briggs is solid state and reliable. Also each coil/plug is a
complete independent ignition and there are plenty of them for free with
rusty contaminated gas tanks  making the carburetors inoperable.

george grimes


   There are kits that convert point to solid state available, Virg