Small Engines (Lawn Mowers, etc.): BRIGGS ANS STRATTON 17.5 INTEK BACKFIRES, briggs and stratton, snapper mower

Question
I HAVE A SNAPPER MOWER WHICH HAS A BRIGGS AND STRATTON 17.5 H.P. INTEK MOTOR.  TO THE BEST OF MY ABILITY I BELIEVE THE MODEL NO. IS 08021ZD474532 ( IT'S HARD TO READ)/  THIS MOTOR HAS ALWAYS BACKFIRED WHEN YOU CUT THE ENGINE OFF.  I WAS TOLD TO CUT THE ENGINE BACK TO IDLE BEFORE CUTTING THE ENGINE OFF.  ALSO RECOMMENDS THIS IN SNAPPER'S INSTRUCTION BOOK.  I WAS  CUTTING THE OTHER DAY WHEN THE LAWNMOVER SIMPLY QUIT.  THE REPAIRS HAVE BEEN MADE AND THE SMALL ENGINE REPAIRMAN SAID THAT THE ENGINE HAD A BENT PUSHROD AND I TOLD HIM ABOUT THE BACKFIRING.  I USED  IT TODAY AND IT STILL BACKFIRES BUT NOT AS MUCH AS BEFORE.  COULD THE BACKFIRING BE THE CAUSE OF THE PUSHROD DAMAGE?  THANKS LAWRENCE

Answer
Your bent pushrod will not be the total cause of the back fire issue Since this engine did this from new, I would be thinking a camshaft may be the problem or a defective anti fire fuel solenoid  The solenoid is the first thing i would look at.  The camshaft affects the timing of the engine.

When the repairman put the new pushrod in, he would have had to readjust the valves which has compensated for the "bad timing" of the bad camshaft.  This is why its not so bad.

I would also be sure the exhaust valve is seating properly.  The reason the engine backfires is because fuel that is unburned after the engine turns off is ignited by the heat of the engine.