You should be OK with a standard (largish) Phillips head screw driver. I took my engine off last weekend without any problems. You must remove the muffler first, followed by the cowling, and then the engine from its mounts. One of the screws is obscured by the carby, but you should be able to get in there. The bolts on the other side should be recessed in and hold tight while you loosen the screws. Try some WD 40 if they stick. You want a Phillips head screw driver with a fairly hefty grip for max turn leverage. If your hand slips on the handle, try using a hankerchef to get more grip. Make sure you are turning the screws anticlockwise!