Are you sure you have the right float needle, Aldo? That float looks way too low, which will cause lean mixture. I think you should look at the things that set the float height: needle length, correct assembly of needle and clip to float arm, and seat position - is it pushed in all the way?
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I may be wrong, but I can't remember ever seeing a simple toroidal carburetor float that was intended to be a long, long way from level. Given that the carburetor has been messed with previously, could the previous tenant have pushed in a Viton seat on top of a metal seat, thinking it should have both, when it shouldn't? If the needle is Viton-tipped, it is unlikely the seat should be Viton as well.