loose valve Optimus 1200

I have an Optimus 1200 that has had the rapid torch removed and replaced. in order to remove it the valve must be rotated counterclockwise for clearance. The valve is loose. How do I get the valve to tighten and install the rapid preheater at the same time?

 

You must replace the lead washer there too if it have been loosened. Unscrew the control wheel if it touches the rapid burner

 

Thank You Matti. I may have to entirely remove the rapid.