Small Engines (Lawn Mowers, etc.): backfire, breather tube, needle valve

Question
I have a 16 hp vanguard B&S 303447 type 1068 engine that backfires at high speed, low speed and sometimes under power.When I first push the throttle for more power it will hesitate and some times under full power it will hesitate. Could it be the needle valve under the float? Or What else could it be.The breather tube from engine to carburetor had cracks in it so installed a new one,but it still backfires.. Thanks for any information. Gene

Answer
   A backfire like you describe makes me think ignition related.
I have seen on the Vanguards that where the coils bolt on the engine,
the metal get very corroded, and the coils have a poor ground and cause trouble.  So you may need to take them off and clean that connection.
   Also, a lean running carb could cause some trouble as well, so if there is a low speed mixture screw, turn it to the left some and see if it improves.
  Let me know what you find.

  Fish