I have a 1997 Polaris sport 400 (2-stroke engine).  Just this year the atv refuses to start all the time.  Sometimes it will start and run great throughout all rpms.  When you shut it off and try to restart awhile afterwards it will not start.  The spark plug has no spark.  Battery is new and the engines gets plenty of fuel.  Have replaced the spark plug. The atv has about 300-400 miles on it ,that's it, it is almost new and spends its time sitting more than running but is well kept and treated (fuel).  I checked the ignition switch by opening it up cleaning it etc.  I did not check the ignition kill switch though. Can this be an intermittent CDI box or what?....Help          Jim