Just found this forum...wished I'd found it earlier, like two years ago when I bought two of those pesky Champion (Williamsburg) toilets.
I, too, am plagued with leaky (and extremely noisy) flush valves. Both toilets are problematic. I have been getting middle-of-the-night phantom flushes (both toilets--different nights, fortunately) due to the leaky valves causing the tank to refill, plus incomplete flushes when I do flush the toilets.
I saw Terry's photos (at least, I think they are Terry's) of the valve seal replacement and of the replacement flush valves. I've done the valve seals bit, with no success. So...I (just) phoned American Standard (800-442-1902), and after a short wait, spoke with a representative who was very courteous and promptly took my name and address. He also asked for the model number (etched inside the tank, starting with a "4" and is 4 digits long, of each toilet--was the same number) and told me they would be shipping me a couple of ("free"!!) replacement flush valves. It was a painless procedure and I didn't even have to complain about the lousy toilet, other than tell him the flush values were no good...and no parts were available to fix them.
I should receive my two replacement flush valves within 10 days, the representative informed me. A big "THANKS" to Terry for this forum and for posting the photos of the replacement flush valve. By the way, I think the American Standard telephone rep was somewhat surprised when I replied to his "the replacement valve will look different than the one you have" that I knew that because I'd seen a photo of one.