The only way to accurately check and set the timing is with a tachometer and strobe after using a degree wheel and pointer to mark the flywheel with a timing mark.

Trying to use the bump on the flywheel is somewhat futile because the air gap and the varying resistances of different pickups makes the trigger point vary. 

Using the mark on the stator screw mounting hole will usually get you within a degree of the correct OEM timing.  The CDI boxes often have a degree variation from CDI box to CDI box