To enable winding the kick start spring I made a tool for this, see pics., you wind the spring it up to its correct tension and then insert the m4 screw, very easy.
There is only one penny washer, my sketch is incorrect, the arrow points to the spring retainer and not the penny washer, sorry for that
The mod does not stop jamming but it gives you the ability to see inside the box whilst you are operating the kick start mechanism to assess what is causing the jamming.
Hope this helps, sorry for the pics. being on their side.