ok there are few reasons why a spark would be happening at the wrong time one is a faulty cdi unit but the most common one is one pf the things i mentioned below and that is a sheared woodruff key on the magneto that keys it to the crankshaft in the right position ,the magneto needs to be removed anyway to get access to the primary ignition coil so you would see then if it was ok as if its not it will be in two pieces.There are two igntion coils though the primary ignition coil is a part of the stator coil assembly which is the one they have mentioned calling it the 'generator coil',there are actually several coils in there including a charging coil a lighting coil and the primary igntion coil,the secondary ignition coil is up the rear of the bike on the left side i think right near the back of the seat under the rear fairing bolted to the frame with one 8mm hex headed bolt.hope that helps a bit for you adam.p.s electrex world would do the stator coil assembly you are asking about which includes the primary igntion coil.
adam bike doctor(of milton keynes motorcycle centre), January 2011