I'll make guess? Engine running poorly (firing on one cylinder is my guess?) Probably not firing on that cylinder. I would pull the spark plug inspect it, check gap, course plug it back in, lay it on metal part of the head, crank the engine see if you getting spark to that cylinder. if so My next move would be see if you got any compression in that cylinder.? probably not? which would next lead to Valve rocker not rocking. (most likely you push rod is bent or fell off the rocker not opening which every valve is not rocking

An excerpt from the bulletin "APSI #: 87 DATE: NOVEMBER 2012 SUBJECT: CYLINDER HEAD TORQUE CHANGE MODELS: 210000 280000 310000 330000 OHV VERTICAL SHAFT ENGINES" "Briggs and Stratton recently changed to a new design cylinder head bolt for model 210000, 310000, and 330000 OHV engines. The new bolts require a higher torque during installation. At the same time, we have modified the bolt tightening sequence to reduce the chances of head warpage at higher torque settings. To prevent confusion, use only the new tightening sequence and new torque value when servicing both older and newer designs, including the model 280000 OHV. The following procedure will replace what is currently shown in repair manual 276781 Single Cylinder OHV Air-Cooled Engines."

I believe tomplum has it right. I just went through this last year with the same engine in a Cub Cadet. Same symptoms with oil oozing out of the fuel pump when running. New head gasket solved the problem.

ab26, if your engine has a "fuel solenoid" in the carb bowl, you should shut your engine off at high RPM by turning off the IGNITION SWITCH. The solenoid has a plunger valve that shuts off the flow of gasoline to the MAIN JET. The solenoid is used to prevent the phenomenon known as "afterfire" (which is what you heard). It works like this: If you shut off you engine by moving the throttle to the idle/off position, you kill the spark ignition but gasoline continues to be fed to the intake of the engine (because the solenoid is still energized). This fuel air mix is now just passing through the cylinder and out the exhaust valve without ever combusting in the cylinder. The exhaust pipe and muffler are saturated with extreme heat from use. So long as the fuel/air mix is passing through the exhaust system at a pretty high velocity....no "afterfire, or ignition" can occur because the mix is whisked through without being able to heat to the point of spontaneous ignition. BUT, as soon as the crankshaft and pistons stop moving......so does the fuel air mix and at that point the blazing hot surfaces in the exhaust system instantly raise the temperature of the mix to the point of spontaneous combustion and BANG is the result. Now, when you shut down your solenoid equipped engine at high RPM by turning off the IGNITION SWITCH, this is what happens: Turn key off, fuel solenoid closes depriving the engine of its main jet fuel. Engine immediately burns the last puff of fuel mix in the normal fashion (because the spark ignition is still firing the plugs). As the last of the gas is burned, the engine RPM sudenly dives toward zero, all the while the engine is being purged and ventilated by the air that continues to flow (minus fuel of course) through the engine and out the exhaust. Because fuel is absent, when the engine finally stops at zero RPM under these conditions, there can be no "afterfire" bang.