When complaints indicate inadequate tank venting which possibly has a negative impact on engine function (EFI models are particularly susceptible to this), we recommend checking that the ball of the breather valve can move freely. If this is not the case, slight soiling may be the cause. For this reason, a metal ball is now used in the breather valve instead of a plastic one. The heavier metal ball is less likely to jam due to dirt particles. If cleaning does not fully restore freedom of movement of the valve ball, we recommend replacing the entire filler cap.