Float pin in lawn mower carburetor works loose

I seek a solution to remedy loosening float pin in Craftsman Lawnmower (about 18 mos. old). The carburetor is plastic. Pin that hold the float works loose. I welcome suggestions. Any chance this is a design flaw that Sears will correct? Thanks. I know one of you mechanical geniuses will have an answer.

Float pin in lawn mower carburetor works loose