Ryu, I'd say the 2240 was not loaded properly if it ran hot. Those motors work well in 1/5, so a 1/8 truggy, unless you're doing speed runs, is a little on the light side. If you can get your hands on a 1950, with an appropriate kV, that would work much better. I had a Basic XL 2800 kV in my aluminum Rustler and it ran hot on 4s, even geared for 80mph. I didn't want to go any faster, though.
