Parts such as the Carburetor: Float Set, Jet,main #55, Jet,slow.#35, Tube,fuel 3.5x240 are included in the St50 Dax European Direct Sales Carburetor parts fiche.
On this parts fiche the Screw,cross 3x5 is the most specified component.
The Screw,cross 3x5 is the cheapest item from this partsfiche.