ORIGINAL: Mustang Fever
Superdo9:
If you're using a 40 size engine and the tank that came with the TT40 (which is a 9 oz), you should be ok, BUT...
I have noticed that on most of the trainers, it is very difficult to get the tank high enough in the airplane. Ideally, the centerline of the tank (top to bottom) should be lined up with the spray bar in the carburetor. If it is significantly lower, then the engine will tend to starve for fuel during the second half of the tank.
You might have better luck getting the Hayes slimline 8 oz tank, as it is very short (top to bottom) and can be got higher up into the fuse. Alternatively, try remounting the engine so that it is sideways in the airplane. This cures all tank alignment problems.
I knew someone would say this but this actually wrong. It will work fine if the centerline of the tank is even with the spray bar but the actual ideal location is with the centerline of the tank about 1/4 to 1/2 inch below the spraybar. This is because when inverted the muffler pressure vent is now below the fuel which reduces the tank pressure, the correct location when inverted is the same distance above the centerline to make up for the reduced pressure. Most ARF''s including trainers are fine, but sometimes when oversizing the enginethe carb is too high.