Small Engines (Lawn Mowers, etc.): 15.5 briggs run but pops the whole time through the carb, briggs run, fuel mixture

Question
 hello my 15.5 Briggs its on a poplin rider its a 03 model over head valves it runs but pops through the carob it don't smoke just pops bad i set the valves on 005 but it still pops put a new plug and still pops.the bottom valve moves in and out a good bit the top looks like its not moving in and out as far but its not froze up when i over set the valve it wont start or just back fire not sure what this is should i check the shear pin i cleaned the carob but that did nothing it runs but pops through the carob the whole time and makes the motor sound loud let me know what you think i should try thanks

Answer
Randy

I am not sure you set the valves correctly, I am thinking you may have tried to set the valves without ever moving the flywheel in between the setting of the two cylinders. and if you are getting fuel out of the exhaust or carb, I would say that you are not getting fire in that cylinder. and then I am leaning toward the flywheel key being sheared. if the valves are set correctly and the flywheel key is sheared, then it will spit, blow, pop, and puff. because as the piston comes up to compress the air and fuel mixture for combustion from the spark plug's spark, it is not in time on the flywheel and coil, therefore, you may be sparking on the intake, exhaust,or power stroke. check flywheel key.