One thing you could check that no one else has mentioned, sometimes when installing the fuel tank the odd person gets a pinch in the fuel line right behind the firewall, it's easy to do.

I have 6 TT's. They all run great, including two .61's. Run TT46's on spad 3D's and practice my hovers, so you need a good reliable engine. The only problem I ever had with one was just recently. Was breaking in a brand new TT46 and after two tanks went flying. The bushing on the connecting rod got totally demolished, eaten away and out the ehaust. Got me stumped. Great hobbies here in Canada has great sevice and replaced the engine free of charge. The only thing that I can figure was that the bushing for some reason held on the crank shaft and turned within the connecting rod, eating itself to pieces. The engine looked brand new (it was) and was not over heated in any way. Anyway......... great engines and not the last one I buy.

Peter