After 30 seconds to a minute of lapping, wipe the taper on the crankshaft and the inside taper of the flywheel with a rag to remove all of the lapping compound.    Look at the tapers, they should show witness marks where the two tapers have been mating.  If it looks like the two tapers are mating well place the flywheel on the crankshaft and use the same lapping motion for a few seconds with out any valve grinding compound (dry lapping metal to metal).  Dry lapping will break down any abrasive compounds that me be embedded into the surface of the tapers,  Wipe the tapers clean and place the flywheel on the crankshaft and feel if the flywheel will rock or wobble on the crank taper.  If any wobble can be felt between the two tapers, repeat the whole process again and again until the two tapers are exactly the same taper.