Hello everybody,
first of all thanks for your support. At the end I bought some spares (spring included) to change parts that were a bit deteriorated. The package arrived yesterday and in the evening I assembled almost everything.
Like AVB was suggesting, the air vane was not free to move due to an incorrect position of the engine cover. This evening I will finish the assembly of last components and I will try to start the engine.
In addition to this I discovered that there is a great manual by B&S that helps you with the servicing of the engines (270962 - Single cylinder L-Head). This is helping me also in the correct positioning of the throttle leverages that in time were lost (due to incorrect maintenance).
I will let you know in the following days if everything is solved.
Cheers,
Gio
