B&S 28M707 starting running erratic and surging all of a sudden then cut off. Found fuel in the oil, so changed the oil and I changed the carburetor to a new one and all new gaskets from one end of carburetor to where everything mounts to engine, including breather gasket. Engine surging and also, engine will now crank without choking, which is unusual, and when you move throttle to full choke, engine does not change at all, where it used to try to stall out as with most any small engine when choked. I checked that the butterfly is actually closing to the choked position and it is. Also put new governor link spring on. Sprayed carb cleaner all around carburetor and manifold but never saw any different smoke color or engine change sound at all. Anyone have any ideas?