The float valve (the pointy thing that moves up and down) has an internal, captive, spring loaded pin on the bottom side. This pin is what actually contacts the tang on the float. When the float moves up and down to cloase and open the valve, the action is "softened" by the spring-loaded pin. Sometimes the pins get stuck in the "fully compressed" position and are not obvious. When you set the float height, make sure the float tang is just touching the pin, and not depressing the pin against the (hidden) spring.
Cool with that explanation?
Kevin