I have the same problem. Replaced all the innards to the toilet and then put 2 gallons of water in it to see if there was a leak (didn't hook up water line). Left for an hr and the 2 gallons were gone. No leakage on outside of tank so I figure it must be the flapper but that whole assy is new. Getting rather frustrated and would rather use the backyard as a bathroom before paying the plumber $200 (actual quote)

Hey Bill,
Hi and Welcome to The Plumbing Page. At AskMeHelpDesk.com. You're responding to a 4 year old dead thread so I gave you one of your own. Look in then upper left hand corner of the first post form the date before you post, Thanks,
Before you go potty in the back yard let's get your toilet up to speed.
Check the tank water level, it should be at the mark in the tank or 3/8 to 1/2" below the top of the over flow tube. Now look at the flapper, If it has wavy edges on the flat surface, replace it. The linkage between the flapper and the flush lever should have 1/4" play when the tank is filled. Sounds like your flapper linkage needs adjusting.
With the flapper seated the linkage wants to have 1/4" of play. Too much play and the flapper doesn't get pulled back enough giving you a short flush. Too tight and it lets water seep past the flapper. I adjust the chain by the link and if it needs fine tuning, I bend the flush lever rod a bit until I have the desired play in the linkage. One more thing about a flapper. You will see where the old flapper hooks onto the base of the white overflow tube. On a older type with no hooks the flapper has a ring that slips down over the overflow tube to the seat,(see image). If your tank has hooks, take a sharp knife or scissors and cut the neoprene ring off on the marks provided and hook the flapper on the hooks. Leaving the ring on will interfere with the flush. Also, check the small tube coming out of the top of the ballcock and make sure it's connect to and draining into the white overflow tube. If the leak is at the base of the tank there are two brass bolts on both sides of the flapper, if the tank is loose, leaking or wobbly, snug up the bolts. If there is dampness at the base of the bowl, pop off the china caps and snug down the closet bolts. I would check all this out before paying 50$ for a service call and 50$ a hour thereafter. More questions? I'm as close as a click. TOM