The first thing that comes to mind is that there is excessive fiction loading up the motor. This could be between the motor pinion & main gear, or the tail belt is too tight, causing excessive draw on the motor & ESC, making them HOT.

Check your gear mesh between the motor pinion & main drive gear. You should be able to take a strip of paper (about .0035" thick), and feed it inbetween the main gear & pinion. It should come out the other side with neat folds, if it doesn't fit thru, or tears are on paper, the mesh is too tight readjust the motor pinion to gear. If the paper comes out with only slighly crimpled, the mesh is too loose, readjust.
A simple way to adjust gear mesh is to slip the paper inbetween the main gear & pinion, then push the motor up snug to the paper & tighten the bolts, then check the paper.
Next check the tail belt tension, it should be tight enough so the belt doesn't slip on the tail belt pulleys but not so tight that it loads up the tail belt drive, belt too tight. I normally press on the belt just behind the drive assembly it should deflect about 1/4" or so. If you hold the main gear so it doesn't move & turn the tail rotor you should feel the belt deflect but not slip on the tail pulley.
To adjust the tail belt tension move the tail gear housing forward just a bit, you may have to move the tail servo mount forward the same amount, otherwise your tail blade pitch & gyro will be out-of-whack.

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