Abstract: A locking cap for closing the oil fill opening of the crank case in a motorcycle engine. The cap has only three major members. A first member has an upper grip portion and a lower portion with openings located in the lower portion for holding ball bearings. A second member is located within the first member and is rotatably coupled to the first member. A lock mechanism attached to the first and second members rotates the second member relative to the first member as the lock mechanism is operated to urge the ball bearings to move through the openings in the first member as the second member is rotated in a first direction relative to the first member. A third member attached to the second member provides support for a dip stick.