The welding rod should fit snugly. Before installing it I heat one end with the TIG torch to create a little ball of metal on one end to prevent the pin from coming out. Then I insert the pin in the gear/shaft so that it protrudes out the other side about 1/8". Then I heat that end with the TIG electrode to form another molten ball on that end also, permanently locking the pin in place. Be sure that the ends of the pin do not stick out more than the root diameter of the gear teeth or you may have trouble installing it past the cam gear.
You can also grind down the longer pin, but I would take care not to heat it up so as to lose its heat treat.
DO NOT use drill rod as it is too brittle and may break. Good luck.
