I have a smallish oil leak which Is from the bottom of the crankcase. I intend to clean it up and try a wee touch of sika flex on to see if it will hold it back. However I notice there’s one set screw down low just off the centre at the front of the engine (rather than a bolt). It’s in this area it’s leaking, however adjacent is a small black wedge type semi circle of metal, which rests within the casting, not sure what this is for and whether it can be temporary popped out prior to sealing?