Why does my quad backfire?


My atv back fires really bad. Gets worse the warmer the engine gets and also backfires the most during deceleration when I let off the throttle. Any ideas? {John, OK 2004 John Deere 500 Buck Auto}


Your engine is running extremely lean causing it to backfire. Have you recently changed your exhaust system, muffler or air filter? Anything that increases the air flow can lean out the engine. Even washing your K&N or Uni air filter and not re-oiling it can cause your quad to backfire.

Please review our pages on changing your exhaust system. and carburetor jetting page 1 or page 2. If you aren't familiar with jetting and what the different sizes of carb jets can do to improve or impede your engine performance, start with the Carb Jets page.  

Another cause of backfiring can be weak spark. If your Buck had weak spark you would also see some black smoke. You did not mention smoke, but if that is also a symptom, review this page on charging systems.

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