1921 hudson starting

Unknown

I am ready to start my 1021 hudson but I have a problem. I had the combination starter generator off and had it checked out. It's okay, and I can turn it on in preperation to stating, but if I hook up the shaft with the water & oil pump it will not turn. I can put preasure on it and stop the shaft when its not hooked up to anything, and yet if I don't hook it up to the shaft it will spin the engine just fine, any trouble shooting out there to help me. wayneerickson