That slot should not be empty. On mine the 20 amp headlight fuse goes there. Take a look at the underside of the fusebox cover and it will tell you what fuse goes where, if it indicates empty in that slot then you are fine, but I doubt it will. In any case, if a fuse is supposed to go there put one in.
Have you cleaned the connection at the starter? If not pull it out and check for crud and then file and clean it good. Also, try bridging the clutch safety switch with a wire in order to bypass it, so as to rule that out too. I soldered in a permanent bypass. I just got tired of having to fuss with that fickle thing.