Why would a lawnmower engine leak oil out of the carb into the airfilter?

can anybody help me with this? i found the lawnmower out in the trash got it to work but then found this problem later the mower still runs fine except for this problem i whiped down the filter compartment and the engine and couldnt get it to leak again. this was when i had tipped the lawnmower before i was about to do an oil change on it but i had not yet touched any parts and the oil cap which is located on top next to the gas cap was on tight and then i checked the drainplug located under the mowing deck to see if it was tight and it was also. this is a briggs and stratton 6.5 hp engine on a craftsman lawnmower.Why would a lawnmower engine leak oil out of the carb into the airfilter?
it will do that if you turn it over, clean or replace air filter and run until it burns all the excess oil out, it will smoke for a few minutes then it should be fineWhy would a lawnmower engine leak oil out of the carb into the airfilter?
Most lawn mowers use a foam filter that is supposed to have motor oil in/on it to help filter. This could be the case, or, if it was tipped up long enough it could have seeped thru the cylinder and intake valve
If oil level is too high in the crank case it will show up in the carb %26amp; filter.
The best thing I can tell ya is, ask a local craftsman dealer or get the number to B%26amp;G, %26amp; ask them.
briggs is a damn good motor, but it will leak oil if it was turned upside down.