I have a bike motor that ive built on my cruiser, I came to the last and most annoying part on the motor. There are 3 screws that wont budge no matter how hard i tug to get em loose. The screws hold the Crank shaft sprocket cover. Ive already tryed WD 40 and Engine Greese. The Rust must be deep in the philips screw. Ive drilled and tugged on it so much the head of the screws are eaten up. Whats the best and fastest solution for me?