I am using this motor:
http://www.hobbycity.com/hobbycity/s...idProduct=4659
It is also available with 900kv and 770kv, the size is ideal for the CRT.5
I think for my 1000kv motor, 4s with small tires or 3s with large tires is great. It is so powerful, it's wheeling all the time even when i'm driving around with around 25mp/h it's easy to let it wheely.