OK, that is what I call the timing cover (because the timing gears are behind it), but Briggs & Stratton call it the crankcase cover. Once you take out all of the screws, it will come off but usually the gasket tends to hang on to both parts. Removing the cover without damaging the gasket may not be possible: it is likely to split, or part of it sticks to each part of the engine and tears when the parts are separated.
My method is to tap around the outside of the cover gently with a soft-faced hammer. If it doesn't come loose (and it may not) I apply the sharp edge of a knife blade to the joint line, and gently tap the back of the knife with a hammer. Be gentle with either approach: you want to end up with the mating metal faces undamaged, and they are only cast aluminium.
