MK111 timer mod

I want to change my timer now so that it just does a 20 second on pulse and then turns off until power is reapplied. What is the best way of doing this?

That is not possible with this kit.
We’d recommend VM141
http://www.vellemanprojects.eu/distributor/products/view/?country=be&lang=en&id=369866

Sussed it.

Removed 1M pot and R2, changed cap 3 for 1000uF and it works.