Where did you  get your  jets from. If you  bought a carb rebuild kit that dont mean its all right. I would  tear the carb down and drop it in a can of chem dip . Clean it all off with a can of carb cleaner, chase every passage  with air. then look at the jetting with the magnifying glass. Just to make sure it has the.correct jetting.. then make sure the air cleaner is clean and  trim both ends of the plug wire.  That should do it.  I  put a br8eix in mine after i rebuilt the entire  engine.  It has about 9 weekends  of hard riding  on it from near 100 at the dunes to 20 degrees out. I haven't  put a new plug in mine since i got done tuning it. Plug color is perfect mixing mine at 32:1 with 93 octane  and amsoil dominator.  As someone else said tuning is done with the fuel curve and the timing  curve . Any other method is a  cover up.