I always have wondered why engines backfire any reasons? Luckily just my lawnmower does this so far.

 

at what point does it backfire?.. just while running?.. when youre shutting it down?.. under load?.. hot? cold?... usually its improper fuel mixture/incomplete burn.. Sometimes its leaky exhaust valves.. Be more specific....

 

Why do engines backfire?

Mechanics have told me backfiring usually indicates a fuel-lean fuel-air mixture.

While ATVing, I've noticed backfiring on different machines sometimes when shutting down the throttle, transitioning to idle, maybe while descending a hill under engine compression braking.

These examples of transient backfires while the engine is not under load do not pose serious problems; often, such a backfiring condition can be eliminated by backing out the carburetor idle mixture screw slightly.

Tree Farmer

 

Improper Fuel / air mixture Some rev limiters have been the cause .and in the case of most four strokes the timming is off.or dirty points on older machines,AND LAWNMOWERS.....hardlydangerous1@yahoo.com

 

It is probably your throttle. Mine had to be replaced when I bought it just for that reason. jThere is some kind of electronic device in the throttle body that causes miss timing. Call a reputable dealer and he should tell you this. Had mine replaced and it was fine after that.

Jaybee

 

It only backfires when I shut it off.
Thanks for the replies