Rebuilt the starter on my 52 and...have the same problem. So I looked at the linkage as 52Carl suggested. Loose and worn at several points. Welder will get warmed up. Yep a bottle cap worked for me as well. Looking at the linkage, more welding and grinding to fix than I want to do. So I will just "reface" the arm that pushes the "button". Removing the starter is easy. Pulling the "button/switch" is 2 screws. Zap a bump with the wire welder is not too bad. Adjusting the "bump" if the starter engages before the bendix drive is in the teeth of the flywheel is my only concern. That bottle cap is not very thick so not much will be needed. With out the welder, I might be tempted to use JB Weld to build p the face of the arm on the starter. Not a lot of force and no side loads to break it off. That might just work.
