I just went thru this with my 2001 warrior had no spark,i replaced pick up coil 1st .Then i would get one spark after i would turn key and switch off .I replaced the whole stator assemblby and it fired right up 55 bucks you cant go wrong.4 days in the mail.Here is link
http://zoomzoompartz.highwire.com/product/1993-1998-yamaha-kodiak-400-2x4-4x4-atv-magneto-stator-coil....Zoom Zoom parts is website click on warrior link.wiring harness is exact match and took about 30 minutes to change out.Use an impact screwdriver and good luck