Briggs and stratton problem

Most B & S engines have a crankcase breather tube running from the engine to the carburettor so oil will probably have run through it into the carb. Remove the spark plug and air filter, crank the engine over several times to get most of the oil in the cylinder and carb out. Make sure the plug electrodes are not fouled with oil and replace it in the head. Check the oil level and top up if needed then try to start the engine, some oil smoke will probably ensue but should clear in a few minutes.  Before refitting it, check the air filter for oil, if it is contaminated, a foam filter can just be squeezed until most of the oil has come out. An oily paper filter will need replacing.