back firing through carb

[DavidCollieryfz]

my yfz is back firing through the carb sometimes when i try to start it if its not backfiring its sounding like it under the seat it did it so hard today i thought it knocked off the air filter , it didnt but it but sounded awful any ideas

[biggen]

might be your timing is off i would have it checked before it blows something

[400exrider36]

my 400ex used to do that, scared the $#!T outta me,. not sure what it was from tho...it was sick at the moment