Setting the carburettor float at the correct level will ensure no annoying fuel leaking from the overflow pipe, and therefore improving economy - replace this with ALL the other wear items like main jet, needle jet and slow running jet, starter plunger and this PLUNGER
Spring for best results.
A related item:
1341101010
Check the schematic to ascertain which parts are required for a complete carburettor makeover. Fit new gaskets and seals at the same time!