Looking at that photo of the starter I'd definitly have the connections off and clean them. They have to be spotless and tight. I now use the toothed anti shake washers as a matter of course on all the electrical fitting and earth straps, they may feel tight, but still won't work. My WC51 has always been very relaible, a couple of months ago I started her up moved her out of her shed and switched off. Went to restart, totally dead! NADAR! No lights , no indicators no noffink! After head banging I went under to the battery earth strap, looked OK and wouldn't move with hand pressure. As that was the only thing I hadn't checked I took it off and cleaned it then retightned. No problems since.