It's the whole flushing mechanism from the chain to the flapper, but not the handle or lever. On this toilet, it consists of a flapper and above that 2 cylinders each open at one end, placed perpindicular to each other. The cylinders sit below the water line, i.e. they are full of water and when the chain pulls them up, they're supposed to stay up until the top cylinder drains (the top cylinder has a small hole in the closed end which drains at the same rate as the tank). Once it has drained it falls and the flapper drops right at the same time the tank has emptied (so it seals). The problem I'm having is that when I pull the handle it doesn't always pull the cylinders back far enough to make them sit right up (they'll do it sometimes but not others). I figure its just a chain adjustment issue but I've set the chain every which way. The only thing I haven't done is attach the "Y" clip (which also came with the unit I purchased) to the chain. I can't figure out how to attach it, there was no Y clip on it before and I didn't have this problem before (or on my other toilets, which are the same and don't have a Y clip).
I was going to change the handle and lever but the only thing which would seem to help would be a shorter lever and its already the shortest I can find (4"). Maybe if I could make the handle turn more to lift the lever higher?