B&S 15.5hp ohv i/c engine backfiring when trying to start

[MyBallsHurt]

So awhile ago the mower wouldn't start and had been having some problems a few weeks before and i just sprayed carb cleaner, now the engine will not start and backfires loudly. So i thought i should do a value adjustment, everything looked good inside, did the adjustment at 004 on both. It will still not start but does not backfire as loud or as often.

 

[gregjo1948]

So awhile ago the mower wouldn't start and had been having some problems a few weeks before and i just sprayed carb cleaner, now the engine will not start and backfires loudly. So i thought i should do a value adjustment, everything looked good inside, did the adjustment at 004 on both. It will still not start but does not backfire as loud or as often.

It does sound like a valve problem. Check the adjustment on the exhaust. There is a compression release that causes the exhaust valve to be partially open. Rotate the engine and you can see the intake and exhaust both open at the same time. gregjo1948

 

[ILENGINE]

I would also make sure the flywheel key isn't sheared or offset. Strange things can happen sometimes.

 

[choogie62557]

Your cam lobe may be worn off. Check lifter movement.