1969 Evinrude 40 HP Big Twin, Big Twin Electric Lark Service Manual 4596, Page 33Get this manual
When the poles of the flywheel magnet sweep past the first and center legs of the core, magneti flu flow is momentarily established in the coreTh flux temporarily assumes direction through th core from the north pole of the permanent magnet to its south poleAs the poles of the magnet sweep further along the flux in the center leg breaks downThe rapid deve lopment and collapse of flux in the center leg induces an electric charge in the coilsThe current in th primary coil flows through the closed breake pOints and sets up magnetic flux of its own in the center leg of the coreThe direction of the flu momentarily opposes the establishment of reve rse flu in the center leg as the poles of th fl ywheel magnet reach to the center and third leg of th coilAt this precise moment, the breaker pOints are opened by cam on the engine crankshaftThis interrupts th flow of current in the primary current, and the op-
posed flu in th center leg collapsesT haste th collaps e, condens in the primary cir cuit abs orbs the current which would otherwis arc across the opening breaker pOintsThe rapid collaps indu ces current of suffici ent voltage in the secondary cir cuit to arc across the spark plug air gap Th condenser, which acts like storage tank, consists of thin sheets of metal foil separated by insulation, rolled save spac and enclos ed metal caseOne sheet of foil is rounded to the case, the other is connected through insula ed wire the insulated stationary breake pointSPARK PLUGS Spark plugs havihg the proper heat ange are very important for peak operation of the motorThe 40 HP moto rs are designed to operate with M42KJ4J, or