I have been breaking in my TT91 1 quart at a time in the back yard. I've used around 1/2 gallon of the Powermaster up. I went ahead and used it when one guy E-mailed me that that was the only fuel he could get his TT91 to run good on when he was breaking his in. The engine starts with just a flick of the finger. They say before starting to press in the choke and turn the prop clockwise to draw fuel. I found that it's better to press in the choke while trying to start the engine. Starts very quickly that way. I'm getting great compression from the engine. Noticably after the first tank. I checked the clearances of the valves and there both staying put all tight on the nuts. Maybe the Thunder Tiger Quality controll is taking care of it's loose nuts!!
One waga waga is when I take the prop off along with the spacer to where the bearing is showing the main shaft will move back and fourth with a small amount of play. See if yours has this play. Of course when the prop goes on and the nuts are tightened the play will be gone because the shaft is pulled forward.