As has been explained previously, the most common float level check is done with the carby off the bike and held in the horizontal plane, using a piece of tubing on the fuel inlet and gently blowing in the tube while at the same time raising and lowering the float to find the point at which you cannot blow into the tube. The float should be sitting in a horizontal position at that point. If it isn't you need to adjust the tab that locates the needle valve that shuts off the fuel. This is a rule of thumb adjustment only.