Often they quit working properly due to sludge buildup inside the flapper box creating excessive resistance. They can also leak from deteriorated gaskets. Replacement gaskets can be found for pretty cheap, I am not sure on your "new" model. I use a very light grease to lubricate the flapper. You will have to make your own wrench to remove the screws, like below.

[img]http://www.surfacezero.com/g503/data/3176/2014-03-07_19_34_15.jpg[/img]


1941 Chevy 1 1/2-ton WW2 4x4 dump truck
In the Stovebolt Gallery
Lots more pictures