41magnum is it a 1941 HD-20 or a 1946+ HD-25
KC, I checked to confirm, and as I suspected when Scott and I replied laat nite, neither the 1941 HD-20 nor the 1946+ HD-25 manuals/parts diagrams are available at the site you linked.
As a 70+yr old motor, free online parts diagrams are going to be tough to find and extremely unlikely.
HD-20......sorry for the confusion.