Hi Moby Mick, your engine was made on 6 May 2005, and its "manufacturing plant" is not a plant at all, but an administrative center at Briggs' head office. These factors lead me to suspect you have an early Chongqing engine, which in general is not a good thing to have. From what I've seen and heard Briggs did get that plant working properly, but it took several years.
Oil leaks from multiple places simultaneously are often a result of crankcase pressure, typically caused either by excessive blow-by (combustion gases leaking past the piston rings into the crankcase) or an obstruction in the positive crankcase ventilation system. Hence I generally agree with Cyberjack, though I add the possibility that your engine has leaky piston rings due to them potentially being poorly made, poorly fitted, or both. Alternatively the bore may have been poorly machined.
